1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

REVISED
FINAL
VOLUME I
Ecological Risk Assessment
for
Bolsa Chica
Lowlands Project
Huntington Beach, California
1448-10181-97D068(TS)
Prepared for
U.S. Fish and Wildlife Service
Region One
Prepared by
July 2002
Bolsa Chica E062002010SAC

Contents
Section
Page
Executive Summary......................................................................................................................ES-1
Introduction and Project Approach (Section 1)............................................................ ES-2
Problem Formulation (Section 2).................................................................................... ES-3
Analysis (Section 3) .......................................................................................................... ES-3
Exposure Characterization (Section 3.1) ....................................................................... ES-4
Ecological Effects Characterization (Section 3.2) ......................................................... ES-8
Risk Characterization (Section 4) ................................................................................. ES-10
Conclusions and Recommendations (Section 5) ........................................................ ES-11
1. Introduction..................................................................................................................................1-1
1.1 Objectives and Scope.....................................................................................................1-3
1.2 Project Approach ...........................................................................................................1-4
1.3 Guidance.........................................................................................................................1-6
1.4 Assumptions ..................................................................................................................1-6
1.5 Organization of the ERA Report .................................................................................1-8
2. Problem Formulation..................................................................................................................2-1
2.1 Site Background.............................................................................................................2-1
2.1.1 Location/Setting............................................................................................2-1
2.1.2 Climate............................................................................................................2-2
2.1.3 Site History.....................................................................................................2-2
2.1.4 Previous Investigations ................................................................................2-4
2.2 Ecological Characterization..........................................................................................2-5
2.2.1 Identification of Habitats..............................................................................2-5
2.2.2 Identification of Potential Ecological Receptors........................................2-6
2.3 Chemicals of Potential Ecological Concern ...............................................................2-8
2.3.1 Preliminary Data Evaluation .......................................................................2-8
2.3.2 Preliminary Background Evaluation ..........................................................2-9
2.3.3 Preliminary Evaluation of Chemical Contamination.............................2-10
2.4 Assessment Endpoints and Measures ......................................................................2-11
2.4.1 Assessment Endpoints................................................................................2-12
2.4.2 Risk Hypotheses ..........................................................................................2-12
2.4.3 Measures.......................................................................................................2-13
2.5 Ecological Conceptual Site Model.............................................................................2-14
2.5.1 Identification of Representative Species ..................................................2-14
2.5.2 Exposure Pathway Inclusion/Exclusion..................................................2-17
2.6 Biota Sampling in Nearby Areas ...............................................................................2-18
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CONTENTS
3. Analysis......................................................................................................................................... 3-1
3.1 Exposure Characterization .......................................................................................... 3-1
3.1.1 Field Sampling and Analysis....................................................................... 3-1
3.1.2 Data Evaluation............................................................................................. 3-6
3.1.3 Background Evaluation.............................................................................. 3-12
3.1.4 Exposure Analysis ...................................................................................... 3-18
3.1.5 Exposure Profile .......................................................................................... 3-24
3.2 Ecological Effects Characterization .......................................................................... 3-25
3.2.1 Ecological Response Analysis ................................................................... 3-25
3.2.2 Stressor-Response Profile........................................................................... 3-37
4. Risk Characterization................................................................................................................. 4-1
4.1 Risk Estimation.............................................................................................................. 4-1
4.1.1 Sediment /Soil – Terrestrial Receptors ...................................................... 4-3
4.1.2 Sediment/Soil – Aquatic and Semi-Aquatic Receptors........................... 4-6
4.1.3 Surface Water – Aquatic Receptors .......................................................... 4-15
4.2 Risk Description .......................................................................................................... 4-19
4.2.1 Bolsa Bay ...................................................................................................... 4-19
4.2.2 Full Tidal ...................................................................................................... 4-20
4.2.3 Future Full Tidal ......................................................................................... 4-20
4.2.4 Garden Grove-Wintersburg Flood Control Channel............................. 4-21
4.2.5 Gas Plant Pond Area................................................................................... 4-21
4.2.6 Muted Tidal Plus Rabbit Island ................................................................ 4-22
4.2.7 Seasonal Ponds............................................................................................ 4-23
4.3 Uncertainty Analysis .................................................................................................. 4-23
4.3.1 Problem Formulation ................................................................................. 4-24
4.3.2 Analysis ........................................................................................................ 4-24
4.3.3 Risk Characterization ................................................................................. 4-27
4.3.4 Overall Uncertainty .................................................................................... 4-28
5. Summary, Conclusions, and Recommendations .................................................................. 5-1
5.1 Summary ........................................................................................................................ 5-1
Problem Formulation ............................................................................................ 5-2
Exposure Characterization ................................................................................... 5-2
Ecological Effects Characterization ..................................................................... 5-4
Risk Characterization ............................................................................................ 5-4
5.2 Conclusion ..................................................................................................................... 5-6
5.3 Recommendations......................................................................................................... 5-7
6. References..................................................................................................................................... 6-1
Appendices
A
B
C
D
E
Field Sampling and Analysis Methods
Core Logs
Quality Assurance Project Plan
Analytical Data
Background Evaluation
ERA REPORT ii SAC/143368(CONTENTS.DOC)
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F
G
H
I
Bioassay Reports
Bioassay-Derived Effect Levels
Stressor-Response Relationships
Risk Estimates
Tables
ES-1
ES-2
ES-3
Chemicals of Ecological Concern in Sediment/Soil – Terrestrial Receptors
Chemicals of Ecological Concern in Sediment/Soil – Aquatic Plants and
Invertebrates, and Semi-Aquatic Birds
Chemicals of Ecological Concern in Surface Water – Aquatic Receptors
2-1 List of Species Potentially Occurring
2-2 List of Special-Status Species Potentially Occurring in the Bolsa Chica Lowlands
2-3 Site-Wide Chemicals of Potential Ecological Concern
2-4 Preliminary Chemicals of Potential Ecological Concern in Soil, Sediment and Biota
2-5 Detected Concentrations in Soils – 1996
2-6 Detected Concentrations in Sediment – 1996
2-7 Range of Detected Concentrations in Surface Water – 1996
2-8 Detected Concentrations in Benthic Infauna Tissue –1996
2-9 Detected Concentration in Fish Tissue - 1996
3-1 Chemicals Detected in Sediment/Soil, Surface Water, and Biological Tissues
3-2 Summary Statistics for Chemicals Detected in Soil/Sediment
3-3 Summary Statistics for Chemicals Detected in Surface Water
3-4 Summary Statistics for Chemicals Detected in Terrestrial Plant Tissue
3-5 Summary Statistics for Chemicals Detected in Terrestrial Invertebrates Tissue
3-6 Summary Statistics for Chemicals Detected in Stilt Eggs
3-7 Summary Statistics for Chemicals Detected in Small Mammals
3-8 Summary Statistics for Chemicals Detected in Aquatic Invertebrate Tissue
3-9 Summary Statistics for Chemicals Detected in Fish
3-10 Background Levels for Selected Inorganic Constituents in Surface and Subsurface
Sediments (mg/kg dw)
3-11 Exposure Parameters for Bird and Mammal Receptors
3-12 Summary Statistics for Soil-to-Biota Bioaccumulation Factors for Bolsa Chica
3-13 Summary Statistics for Water-to-Biota Bioaccumulation Factors for Bolsa Chica
3-14 Summary of Toxicity Test Results
3-15 Univariate Regression of Amphipod Survival (Number of Individuals) on
Untransformed and Natural Log Transformed Concentrations in Sediment
3-16 Univariate Regression of Amphipod Survival (Number of Individuals) on
Untransformed and Natural Log Transformed Concentrations in Sediment
3-17 Summary of F-tests for Comparisons of Amphipod Mortality Regression Models by
Test Media Adjustment Groups by Analyte
3-18 Univariate Regression of Mytilus Development on Untransformed and Natural Log
Transformed Concentrations in Pore Water
3-19 Summary of LC 50 s and LC 20 s for Chemical Concentrations in Sediment
3-20 Summary of LC 50 s and LC 20 s for Chemical Concentrations in Sediment
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CONTENTS
3-21 Summary of EC 50 s and EC 20 s for Chemical Concentrations in Pore Water
3-22 Correlation Matrix Among Analytes Associated with Amphipod Toxicity That Were
Detected in Sediments
3-23 Summary of Proportion of Variance Accounted for by the First Nine Principal
Components for Analytes Detected in Sediments
3-24 Summary of Correlations Between Principal Component Scores for the Nine Primary
Components and Analytes Associated with Amphipod Toxicity Detected in
Sediment (Only those analytes with significant correlations [p

3-5a Selenium (Se) Values (Including Non-Detects) in Sediments
3-5b Detected Selenium (Se) Values in Sediments
3-6a Silver (Ag) Values (Including Non-Detects) in Sediments
3-6b Detected Silver (Ag) Values in Sediments
3-7 Random Sampling Results for Metals Exceeding at Least One Screening Level
3-8 Random Sampling Results for Metals Exceeding ER-M
3-9 Random Sampling Results for Petroleum Hydrocarbons Exceeding at Least One
Screening Level
3-10 Random Sampling Results for Petroleum Hydrocarbons Exceeding LC50
3-11 Random Sampling Results for Chlorinated Pesticides Exceeding at Least One
Screening Level
3-12 Random Sampling Results for Chlorinated Pesticides Exceeding ER-M
3-13 Random Sampling Results for PCBs Exceeding at Least One Screening Level
3-14 Random Sampling Results for PCBs Exceeding ER-M
3-15 Random Sampling Results for Phthalate Exceeding at Least One Screening Level
3-16 Random Sampling Results for Phthalate Exceeding LC50
3-17 Arsenic in Sediment vs. Amphipod Toxicity
3-18 Barium in Sediment vs. Amphipod Toxicity
3-19 Chromium in Sediment vs. Amphipod Toxicity
3-20 Lead in Sediment vs. Amphipod Toxicity
3-21 Nickel in Sediment vs. Amphipod Toxicity
3-22 Aldrin in Sediment vs. Amphipod Toxicity
3-23 Chrysene in Sediment vs. Amphipod Toxicity
3-24 4,4'-DDE in Sediment vs. Amphipod Toxicity
3-25 Low MW PAHs in Sediment vs. Amphipod Toxicity
3-26 Phenanthrene in Sediment vs. Amphipod Toxicity
3-27 TPH Diesel in Sediment vs. Amphipod Toxicity
3-28 Waste Oil in Sediment vs. Amphipod Toxicity
3-29 Arsenic in Pore Water vs. Mytilus Toxicity
3-30 Lead in Pore Water vs. Mytilus Toxicity
3-31 Acenaphthene in Pore Water vs. Mytilus Toxicity
3-32 BHC alpha in Pore Water vs. Mytilus Toxicity
3-33 Chrysene in Pore Water vs. Mytilus Toxicity
3-34 Endosulfan Sulfate in Pore Water vs. Mytilus Toxicity
3-35 Fluorene in Pore Water vs. Mytilus Toxicity
3-36 High MW PAHs in Pore Water vs. Mytilus Toxicity
3-37 Total PAHs in Pore Water vs. Mytilus Toxicity
4-1 Selection of Chemicals of Ecological Concern
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Executive Summary
The Bolsa Chica Lowlands are located in Orange County, California and comprise
approximately 1,200 acres of estuarine, marine and upland habitat. Since the 1920s, much of
the area has been used for oil and gas exploration, production, and processing. The site and
adjacent areas have also been used for agriculture, cattle grazing, as a wildlife refuge, and
for recreational hunting and fishing. The historical site activity as well as urban runoff
draining into the Lowlands has resulted in contamination or physical disturbance of the
plants, wildlife or their habitat on the site.
This Ecological Risk Assessment was conducted in anticipation of proposed clean-up and
restoration of the Lowlands to a functioning estuarine system and to improve wildlife
habitat. It is anticipated that once clean-up and restoration activities are complete, the site
will become a state or federal wildlife refuge, as well as serving as mitigation for habitat
losses elsewhere. The anticipated future use of the Lowlands served as the focus for the
development of the ecological management goals for the site, which are as follows:
• Sediment, surface water quality, and food source conditions capable of supporting
terrestrial, aquatic, and semi-aquatic plant and wildlife populations that would typically
be found in Full Tidal and Managed Tidal coastal wetland habitats, and non-tidal
Seasonal Ponds
• Sediment, surface water quality, and food source conditions supportive of individuals
of special-status biota and migratory birds protected under the Migratory Bird Treaty
Act likely to be found in Full Tidal and Managed Tidal coastal wetland habitats, and
non-tidal Seasonal Ponds
As part of this restoration effort, the nature and extent of contamination on the site is being
investigated and evaluated. Two important elements of the investigation include an:
• Ecological Risk Assessment (ERA) (this document) to evaluate contaminants present at
the site at concentrations that present a risk to fish, wildlife or their habitat. The ERA
identifies exposure pathways and associated site-specific assessment endpoints. The
ERA also characterizes the ecological effects of the contaminants of concern. This and
other information and analysis in the ERA has been or will be used to (among other
things): (a) assess the nature of the contamination at the site and identify the general
areas of the site that contain contamination (b) assess the nature, characteristics, and
sensitivities of the natural resources at the site (c) determine the extent to which the
contamination threatens to impact natural resources at the site and (d) identify the types
or routes of exposure to the contamination that pose an unacceptable risk; and
• Confirmatory Sampling Program (CSP) to delineate the extent of on-site contamination
and the bounds of needed clean-up efforts. (The CSP was not completed at the time of
publication of this report.)
SAC/143368(ES.DOC) ES-1 ERA REPORT
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EXECUTIVE SUMMARY
Two important outcomes of the ERA are identification of (a) chemicals that will be
considered for further evaluation or remediation and (b) chemicals that need not be
considered any further. Chemicals that should be retained for further evaluation or
remediation are referred to as Chemicals of Ecological Concern (COECs) and are listed in
Tables ES-1 to ES-3.
The results of this ERA will be used as a tool used to establish clean-up criteria for portions
of the property affected by on-site contamination. It builds on previously available
information about the site (including ecological and chemical characterization, as well as
planned restoration), which was used to plan and conduct the current work.
Additionally, delineation of boundaries around the contaminated portions of the site will be
completed as part of the future activities including through the CSP and the development of
the remediation plan. It is important to note that this baseline ERA does not assess the
overall areal extent of the contamination, generate or identify remediation goals or clean-up
concentrations, or identify the sensitive habitat areas to be protected from disturbance. The
development of clean-up goals is a complex risk management process that involves an
evaluation of the information contained in the ERA and a range of other factors, such as
technical feasibility and appropriate levels of risk.
In the future, the information and analysis in this baseline ERA will be used as a tool to
evaluate the ecological impacts of alternative remediation strategies and establish clean-up
levels that will protect the natural resources at risk. Possible interim steps also include
removal of hot spots and other interim risk reduction measures.
Introduction and Project Approach (Section 1)
The ecological risks at this site were evaluated using a phased/tiered approach consistent
with established methodologies, adapted to the specific needs of the Bolsa Chica project as
described in the CSP/ERA Work Plan and the revised work plan for the project (CH2M
HILL, 1998a and 2000). The Work Plan as well as the Scoping Assessment (CH2M HILL,
1998b) and Ecological Effects Characterization Report (CH2M HILL, 1999) outline the
various phases of the ERA for the Lowlands and provide preliminary results. The project
approach and content of the various reports are summarized in Section 1.2 of this report.
Specific objectives of this Final ERA Report include updating previous information in the
Problem Formulation (Section 2.0) and Analysis (Section 3.0) portions of this report and
conducting the final phase of the ERA (the Risk Characterization, Section 4.0) using the
results of the ERA Sampling and Analyses, Focused Sampling and Analyses, and previously
available information from the Phase II Environmental Assessment (Tetra Tech, 1996).
The data collected from all those investigations were analyzed and evaluated to help refine
and focus the identification of ecotoxicological risk drivers at the site. The ERA uses a wide
range of commonly utilized tools to evaluate the ecological risks related to site
contamination. Some of these tools include site-specific toxicity tests, site-specific
bioaccumulation tests, statistical analysis, a review of published literature values and
several phases of on-site sampling.
ERA REPORT ES-2 SAC/143368(ES.DOC)
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EXECUTIVE SUMMARY
The ERA report evaluates the risk that the on-site contamination poses to aquatic and
terrestrial plant and animal species that currently use the site and are likely to use the site
after the restoration. The report evaluates potential exposure of receptors to chemicals at the
site through the development of Exposure Point Concentrations and the calculation of
potential dietary exposure of birds and mammals (as doses) through the food chain uptake
model. The Exposure Point Concentrations are a function of chemical concentrations
detected at the site and the manner in which the receptors are exposed to the chemicals. The
report also develops Reference Toxicity Values (RTVs) which are chemical concentrations in
sediment, water, or dietary dosages that are expected to be associated with adverse effects
on biota based on site-specific toxicity studies, site-specific bioaccumulation studies and
published literature values. Finally, the ERA compares the anticipated exposure (the
Exposure Point Concentration or dose) to the RTV (which is a measure of potential harm) to
reach conclusions about which chemicals of potential ecological concern (COPECs) pose a
risk sufficient to retain the chemical for further evaluation or remediation. Chemicals that
are present at sufficiently high concentrations (typically above the RTV) are placed on the
list of Chemicals of Ecological Concern or COECs. Chemicals that are not placed on the
COEC list are not considered to pose an ecological risk at the site, based on available
information, and are not intended to be carried forward for further analysis. A graphical
representation of this approach is shown in figure ES-1.
Problem Formulation (Section 2)
The Problem Formulation section of the ERA presents information that is used to focus the
evaluation of ecological risks at the site. The end product of the section is a preliminary
conceptual site model for ecological risks at the site.
The ERA incorporates and relies on the extensive information already available about
conditions at the site including site background, habitats found onsite, and the results of
previous sampling conducted at selected locations throughout the site. This information is
found in Sections 2.1 and 2.2 of this report.
Previous sampling had indicated that concentrations of a number of chemicals exceeded
levels that could be expected to cause adverse effects in fish, wildlife, or their habitats. As a
result, there was a need for more comprehensive sampling and evaluation of cleanup/restoration
needs. The available information was reviewed to select potential ecological
receptors, determine chemicals of potential ecological concern (COPECs), and identify
pathways through which the receptors could be exposed to the COPECs. The receptors that
were selected included aquatic and terrestrial plant and animal species that currently use
the site and are likely to occur there under future conditions. COPECs identified for further
evaluation were those that exceeded screening-level benchmark values (levels that could be
associated with adverse effects) for sediment, water, or biological tissues. The results of
these evaluations are found in detail in Sections 2.2 through 2.6 of this report.
Analysis (Section 3)
This section presents the technical evaluation of chemical and ecological data to determine
potential for ecological exposure and adverse effects.
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EXECUTIVE SUMMARY
Exposure Characterization (Section 3.1)
The Exposure Characterization contains a summary of the results of the ERA Sampling and
Analyses, Focused Sampling and Analyses, and Phase II Environmental Assessment (Tetra
Tech, 1996). The summary identifies the different types or “suites” of analyses and detection
limits performed on sediment/soil, pore water, surface water, and biota tissue. The
detection limits were chosen to be sufficiently low to allow for meaningful analysis. The
data were evaluated for use in the ERA, subjected to a background evaluation for inorganic
chemicals in sediment, and then used in the various evaluations to develop an exposure
profile and stressor-response profile. These steps are described below.
Field Sampling and Analysis: The preparation of the ERA involved several different
sampling investigations that were conducted throughout the Lowlands. In addition to
sampling conducted in 1996 for the Phase II Environmental Assessment (Tetra Tech, 1996)
and sampling conducted to characterize soil/sediment within the dredge footprint for the
proposed restoration of the site (Kinnetic Laboratories/ToxScan, Inc. and CH2M HILL,
1999), we conducted two main phases of sampling and analysis specifically for the ERA.
These two phases of ERA-related sampling are described below, and the results of all
sampling (including the Tetra Tech investigation and the dredge-material characterization)
are included in the project database that is included as Appendix D of this report.
1. The ERA Sampling and Analyses phase in 1998-1999 was designed to complete
sampling for areas away from known or suspected sources of contamination (“random
sampling” locations), to conduct toxicity bioassays and bioaccumulation studies using
site-collected sediment and water from both “random” and “focused” sampling areas,
and to analyze field-collected biota for chemicals that bioaccumulate.
Random sampling of sediment was conducted by taking samples at a density of about
one core per 4 acres throughout the site, but with at least one core per Cell. (The site has
been divided into units called “Cells.” These Cells vary in size from 1 to over 100 acres.)
For Cells larger than 4 acres in size, up to six cores from contiguous areas within the Cell
were composited to reduce analytical costs. Surface sediment (0- to 6-inch depth) from
these cores was analyzed to evaluate potential exposure of ecological receptors. A subset
of the surface sediment samples also was used for sediment bioassays (using amphipods
and polychaete worms [Nereis]), and for extraction of pore water for bioassays with
bivalve larvae. Subsurface sediments (18- to 24-inch and 42- to 48-inch depth intervals
combined) were analyzed to determine whether buried wastes were present. To obtain
sediment or pore water for conducting bioassays from the Focused Sampling locations,
this sampling effort also included limited sampling from selected locations of the
Focused Sampling program (such as waste sumps, pipelines, maintenance areas, and
stormwater inflow areas).
2. The Focused Sampling and Analysis phase of the ERA occurred in 2000. The program
was designed to allow for more detailed analyses of previously sampled “random”
locations (sampled as part of the ERA Sampling and Analyses described previously),
and to identify the nature of contamination associated with previously identified sources
(such as sumps, wells, pipelines, maintenance areas, etc.) and potential sources. The
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EXECUTIVE SUMMARY
“focused sampling” locations were divided into three main categories that were
sampled as follows:
a) Random Follow-up Sites: Most of the Random Follow-up sampling locations were
re-sampled to a depth of 0.5 foot below ground surface (bgs). If the bottom
composite sample during random sampling exceeded any of the criteria for resampling,
samples were advanced to the original project depth of 6 feet bgs. Only
those constituents that exceeded specified criteria for any particular sample were
reanalyzed.
b) Previously Uncharacterized sites (Clean-up Agreement and Release [CAR] sites):
Sampling of the CAR sites was conducted by taking samples at a density of one core
per acre and analyzing them individually. For those CAR sites that were smaller
than 1 acre, two borings were collected and were analyzed individually. However, if
the CAR site was smaller than 0.1 acre, two borings were collected, the two top
samples were composited together, and the two middle/bottom samples were
composited together for analysis. All borings were advanced to 6 feet bgs. Samples
from each boring were retrieved from three intervals: 0- to 6-inches, 30- to 36-inches,
and 66- to 72-inches. The middle and bottom interval from each boring were
combined into a single sample.
c) Partially Characterized sites: Sampling of the Partially Characterized sites varied
from one kind of facility or feature to another. Sampling rates for all of these sites
were based on the estimated area or linear length of those facilities and features.
Prior to making the final decisions on sampling rates, constituent lists to use, and
depths below the ground surface, all Tetra Tech and CH2M HILL data were matched
to the list of facilities and features. These data were then used to determine whether
any additional characterization was needed. Boring depth varied by site. Surface
sediment (0 to 6-inch depth) from all Partially Characterized sites was analyzed. No
compositing was conducted on any of the Partially Characterized sites.
The results of the ERA will be used to focus the future sampling at the site during
implementation of the CSP. For example, the suite of analytes will be reduced from the suite
used in prior sampling efforts because particular analytes are not found to be of concern to
plants, animals or their habitat on the Bolsa site. In addition, the analysis of information in
the ERA may allow further reductions in the COEC list due to co-locations of chemicals with
other COECs or other factors. Higher detection limits for some analytes may be appropriate
if higher concentrations would be sufficient to detect levels of concern.
The analytical data for soil and sediment were combined as a single exposure medium
because both media will become sediment under the post-restoration habitat types for the
Lowlands, and their character varies seasonally.
Evaluation Areas: The Lowlands were divided into areas with similar habitat types under
current and/or post-restoration conditions for evaluation of potential risks. The specific
Cells included in each area are:
• Bolsa Bay – Inner Bolsa Bay (Cell IB) and Outer Bolsa Bay (Cell OB)
• Full Tidal – Cells 1, 1A, 3 through 8, 15 through 18, 43, 44, 51, 58, 59, 61, and 62
SAC/143368(ES.DOC) ES-5 ERA REPORT
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EXECUTIVE SUMMARY
• Future Full Tidal – Cells 14, 19 through 40, and 63
• Garden Grove – Wintersburg Flood Control Channel – Cell 52
• Gas Plant Pond Area – offsite areas down gradient from the former Gas Plant, south of
Cells 11 and 12
• Muted Tidal plus Rabbit Island – Cells 41, 42, 45 through 50, 53, 55, 60, 66, and 67
• Seasonal Ponds – Cells 2, 9 through 13
• Sitewide (biota only) – terrestrial invertebrates that were composited from throughout
the Lowlands
Background Evaluation: The evaluation of background levels for inorganic constituents in
sediments was completed using samples collected from onsite focused and random sample
locations (including those within the proposed dredge area footprint). Maximum
concentrations of chemicals considered to be background levels in surface and subsurface
sediments and a combined value for all sediments were estimated; this was accomplished
using cumulative distribution plots in which detected and non-detected results were
evaluated together and separately to distinguish the impact of non-detected results on the
distribution and estimated background concentrations. Maximum background values for
the combined data set were estimated for arsenic (11 mg/Kg), barium (110 mg/Kg),
beryllium (0.94 mg/Kg), cadmium (0.66 mg/Kg), chromium (43 mg/Kg), cobalt (10.1
mg/Kg), copper (26.1 mg/Kg), lead (48 mg/Kg), mercury (0.28 mg/Kg), nickel (30 mg/Kg),
selenium (0.54 mg/Kg), silver (0.22 mg/Kg), thallium (0.61 mg/Kg), vanadium (75 mg/Kg),
and zinc (103 mg/Kg).
Exposure Analysis and Exposure Profile: The exposure profile established a relationship
between stressors and potential receptors through: (1) identification of potential sources of
chemical stressors (the COPECs) and their spatial distribution across the site, (2) calculation
of exposure point concentrations for various exposure media and receptors based on the
most likely exposure scenario for each species, and (3) calculation of reasonable maximum
daily dosages for chemical intake through the food chain from abiotic and biotic sources by
terrestrial and semi-aquatic birds and terrestrial mammals.
Sources: The primary sources of COPECs include oil and gas production, non-point source
pollution, and historic farming and hunting activities on or near the site.
Exposure Point Concentrations: A conservative approach was used to define the exposure
point concentrations for receptors in the Bolsa Chica Lowlands. The exposure point
concentrations for abiotic media (intake or contact with sediment/soil, surface water, and
pore water) were calculated based on the mobility of the receptor being evaluated. For
sedentary organisms such as plants and invertebrates, the exposure was based on the
maximum detected concentrations for each detected chemical in each evaluation area. In
contrast, for the mobile receptors such as birds and mammals, the exposure point
concentrations were based on the 95th percent upper confidence limits (UCLs) of the
arithmetic mean. (If a 95th UCL could not be calculated, the maximum detected
concentration was used.)
ERA REPORT ES-6 SAC/143368(ES.DOC)
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EXECUTIVE SUMMARY
Exposure point concentrations for the biota component of the diets for terrestrial and semiaquatic
birds and terrestrial mammals were calculated based on tissue samples collected
throughout each of the evaluation areas. This combination of tissue data was used primarily
because the mobile higher trophic level receptors are not limited to foraging within a single
cell and may forage throughout the site. Tissue concentrations for field-collected terrestrial
plants, terrestrial invertebrates, bird eggs, small mammals, and fish were combined based
on tissue type. A 95th percent UCL of the arithmetic mean was then calculated for the
combined tissue group. However, different species of field-collected aquatic invertebrates
were not combined because different representative species would not feed on all the aquatic
invertebrates collected. The exposure point concentration for each aquatic invertebrate
species was either the 95th percent UCL of the arithmetic mean or the maximum detected
value, following the same rules as were applied to the other exposure media.
The use of maximum exposure concentrations as described above was carefully considered
along with the less conservative alternative approach of using the 95th percent UCL of the
mean. The selected approach is consistent with standard practice. Plants and invertebrates
are immobile or relatively sedentary receptors – it is not reasonable to assume that they
spatially average their exposure over the medium in which they reside (Suter et al. 2000). To
determine which chemicals at the site may require clean-up, the maximum concentration is
the most appropriate exposure measure. This approach is particularly appropriate at this
site because the site is intended to serve as mitigation habitat, and because it will become a
wildlife refuge once remediation is complete.
Food chain uptake or exposure: Contact with chemical stressors by various receptors must
take into account various exposure areas and pathways. Exposure point concentrations for
abiotic (sediment/soil and surface water) and biotic (field-collected plants, invertebrates,
bird eggs, small mammals, and fish) exposure media were calculated based on the most
likely exposure area and pathways for selected representative species. These species and
pathways include:
• Terrestrial plants – Direct contact via root uptake from sediment/soil
• Terrestrial invertebrates – Direct contact with and ingestion of sediment/soil
• Belding's savannah sparrow – Ingestion of terrestrial plants, terrestrial invertebrates,
and sediment/soil, and surface water
• American kestrel – Ingestion of terrestrial invertebrates, small mammals, and
sediment/soil, and surface water
• Black-necked stilt – Ingestion of aquatic invertebrates, sediment/soil, and surface water
• Least tern – Ingestion of fish, sediment/soil, and surface water
• Black-crowned night-heron – Ingestion of aquatic invertebrates, fish, small mammals,
sediment/soil, and surface water
• Western harvest mouse – Ingestion of terrestrial plants, invertebrates, sediment/soil,
and surface water
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• Coyote – Ingestion of terrestrial plants, bird eggs, small mammals, sediment/soil, and
surface water
• Aquatic plants – Direct contact via root uptake from sediment/soil and surface water
• Aquatic macroinvertebrates – Direct contact with and ingestion of sediments/soil
• Fish – Direct contact with surface water
Reasonable maximum daily dosages were calculated for intake of the exposure media
mentioned above by terrestrial and semi-aquatic birds and terrestrial mammals.
Ecological Effects Characterization (Section 3.2)
The Ecological Effects Characterization focused on (1) evaluating site-specific effects data to
determine the potential adverse effects that may result from different concentrations of
chemical stressors, and (2) establishing a link between these effects and the assessment
endpoints and ecological conceptual site model. The product of this portion of the ERA was
the stressor-response profile that was combined with the exposure profile (described above)
to conduct the Risk Characterization.
Site-specific effects data that were evaluated consisted primarily of toxicity and
bioaccumulation bioassays. The toxicity bioassays were used to evaluate responses to the
mixture of chemicals present in sediment, pore water, or surface water. The bioaccumulation
bioassays were used to evaluate the potential for significant bioaccumulation of chemicals
from sediment into the food chain. The results of sediment and pore water bioassays were
also combined with the corresponding chemical analyses to calculate effect levels through
regression analyses. Toxicological information from literature sources, toxicity databases,
and wildlife toxicological reviews was also reviewed for terrestrial and semi-aquatic
receptors to identify RTVs for each chemical and representative species.
The toxicity bioassays were conducted with marine amphipods and polychaete worms
(sediment); bivalve larvae (pore water); freshwater (Ceriodaphnia) and marine (Mysidopsis)
invertebrates, and topsmelt fish (surface water). The test species were placed in sitecollected
sediment, pore water, or surface water for a defined period of time that was
considered to represent an acute or chronic exposure. Endpoints measured included
survival and reburial for amphipods; survival of worms; survival and larval development
for bivalves; survival and growth for fish; survival and reproduction for Ceriodaphnia;
survival, growth, and fecundity for mysids. Results of the toxicity bioassays are
summarized below:
• Sediment – Amphipod survival ranged from 0 to 98 percent; reburial ranged from 22 to
100 percent for those samples with surviving amphipods. Polychaete worm survival was
not significantly affected in any of the tested sediments. Results were further evaluated
using regression analyses (described below).
• Pore water – Bivalve larvae No Observed Effect Concentrations (NOECs) for survival
and development ranged from 0.098 to 100 percent of the test sample. Lowest Observed
Effects Concentrations (LOECs) for survival and development ranged from 0.2 to
100 percent sample. The EC 50 and LC 50 measurements ranged from 0.17 to 100 percent
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EXECUTIVE SUMMARY
sample. However, many of the lower sample percentages were the maximum tested
concentrations as a result of salinity adjustments that were made to bring the pore water
samples into the tolerance range for the tested species. Results were also further
evaluated using regression analyses (described below).
• Surface water – Topsmelt survival and growth were not significantly affected by any of
the tested surface waters. Ceriodaphnia NOEC for survival and reproduction was
50 percent sample and the LOEC for survival and reproduction was 100 percent sample.
The Mysidopsis showed no toxic effects and the NOEC for survival, reproduction, and
fecundity was 100 percent site sample.
Bioaccumulation tests were conducted using polychaete worms and site-collected
sediments. The results of this testing showed that there was significant bioaccumulation for
several inorganic and organic analytes, as follows:
• For inorganic analytes, significant bioaccumulation was observed for barium, cobalt,
copper, lead, mercury, nickel, selenium, vanadium, and zinc.
• For pesticides and PCBs, significant bioaccumulation was observed for BHC (beta and
gamma), chlordane (alpha, gamma, and technical), 4,4’-DDD, 4,4’-DDE, dieldrin, and
Aroclor 1254.
• For PAHs, significant bioaccumulation was observed for acenaphthene, anthracene,
chrysene, pyrene, and fluorene.
Simple linear regression analyses were performed to determine which chemicals in
sediment and pore water best explained amphipod and bivalve toxicity bioassay results.
The toxicity bioassay results were combined with the corresponding chemical analytical
data for sediment and pore water for each test replicate to determine whether a doseresponse
relationship was present and to estimate site-specific survival LC 20 and LC 50 for
amphipods exposed to sediment, and larval development EC 20 and EC 50 for bivalves
exposed to pore water.
In addition, correlation analyses were conducted to determine whether concentrations of
many chemicals were correlated with each other in sediments. It was found that chemicals
tended to occur in groupings, such as metals, petroleum-related compounds, and
organochlorines (pesticides and PCBs). However, concentrations of chemicals in pore water
were not significantly correlated with their concentrations in the sediment from which the pore
water was extracted. This lack of correlation reduces the ability to predict pore water toxicity
to receptors (such as bivalve larvae) on the basis of chemical concentrations in sediment.
The stressor-response profile was the end product of the Ecological Effects Characterization.
This profile established a link between receptors and potential adverse effects. Site-specific
information from toxicity bioassays, bioaccumulation studies, and regression analyses, as
well as literature toxicity information, were used to develop a list of reference toxicity
values. These values are presented in Section 3 of this report and are summarized below:
• NOECs, No Observed Adverse Effect Level (NOAELs), LOECs, Lowest Observed
Adverse Effect Levels (LOAELs) (see Acronyms and Abbreviations) and other toxicitybased
endpoints – Obtained from the literature for terrestrial receptors (plants,
invertebrates, birds, and mammals)
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• LC 20 and LC 50 for survival of aquatic invertebrates in sediment – Derived from the
regression analyses conducted on amphipod toxicity bioassay results
• NOECs for survival of aquatic invertebrates in sediment – Calculated from polychaete
worm toxicity bioassay results
• EC 20 and EC 50 for larval development of aquatic invertebrates in pore water – Derived
from the regression analyses conducted on bivalve toxicity bioassay results
• NOECs for survival and growth of fish in surface water – Calculated from fish toxicity
bioassay results
• NOECs and/or LOECs for survival/growth, reproduction, and/or fecundity of aquatic
invertebrates in surface water– Calculated from Ceriodaphnia and Mysidopsis toxicity
bioassay results
Risk Characterization (Section 4)
The Risk Characterization presents the evidence linking COPECs to potential adverse effects
in the Lowlands including calculation of HQs and evaluation of site-specific toxicity
bioassays and bioaccumulation studies to provide a weight-of-evidence for potential risks
and identify COECs. The identification of COECs is presented in Figure ES-1. All COPECs
that exceeded any available RTV as well as chemicals that showed significant
bioaccumulation in Nereis clam worms were retained as COECs. The overall risk posed by a
COEC in a given medium and evaluation area was determined based on the types of RTVs
that were exceeded (i.e., no-effect levels vs. low-effect levels and chronic effect levels vs.
acute effect levels). The overall risk categories were defined as follows:
• Unknown – RTVs were not available, so risk could not be quantified.
• None – Exposure does not exceed any of the available RTVs.
• Uncertain – Exposure exceeds a no-effect level, but risk could not be fully quantified
because a low-effect level was not available (Category U).
• Some Possible Risk – Exposure exceeds a no-effect level, but not a chronic low-effect
level (Category C).
• Possible Risk – Exposure exceeds a chronic low-effect level, but not an acute effect level
(Category B).
• Probable Risk – Exposure represents the highest level that could be quantified. Exposure
exceeds an acute effect level or showed significant bioaccumulation in Nereis clam
worms (Category A).
The COECs in each medium for terrestrial and aquatic receptors are presented in Tables ES-
1 through ES-3. The chemicals in sediment/soil showing potential for risk to terrestrial
receptors consisted of metals, PAHs, and potentially dieldrin (Table ES-1). The highest level
of risk that could be quantified for terrestrial receptors was Category B (possible risk)
because RTVs were limited to chronic no-effect and low-effect levels; acute RTVs were not
identified.
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EXECUTIVE SUMMARY
The chemicals in sediment/soil that showed the highest potential for risk (Category A) to
aquatic receptors included metals, pesticides, some PAHs, and TPH-diesel and waste oil
(Table ES-2). In addition, significant bioaccumulation of metals and pesticides in Nereis
clam-worms was observed for several evaluation areas. All COECs that also had significant
bioaccumulation were considered to pose a probable risk (Category A) based on
comparisons to RTVs, with the exception of lead and vanadium in the Full Tidal area. These
chemicals were estimated to pose a possible risk (Category B) to aquatic receptors.
The chemicals in surface water that showed probable risk (Category A) to aquatic receptors
were limited to copper and endrin as these two chemicals were the only ones that exceeded
the CA-WQS acute level (Table ES-3). Possible risk (Category B) was estimated for several
other metals, pesticides, and TPH-diesel and waste oil.
Conclusions and Recommendations (Section 5)
The overall conclusion to the ERA is that several chemicals pose various levels of risk to
terrestrial and aquatic receptors. Most notably, metals, pesticides, PAHs, and TPH-diesel
and waste oil consistently show possible (Category B) and probable (Category A) risks to
receptors.
COECs identified in each area of the Lowlands are recommended for further evaluation or
remediation. Clean-up goals should be developed for each COEC based on the receptors
that may be at risk. Once clean-up goals are drafted, the extent of contamination exceeding
clean-up goals within each area should be determined so that clean-up efforts will focus
only on those areas or portions of areas that cause risk.
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SECTION 1
Introduction
This report presents the baseline Ecological Risk Assessment (ERA) for the Bolsa Chica
Lowlands. It provides a qualitative and quantitative evaluation of the actual or potential
effects of chemical stressors related to historical activities on aquatic, semi-aquatic, and
terrestrial biota (plants and animals) that inhabit or may use the Lowlands. The results of
the ERA will provide the information necessary for the state and federal resource agencies
to recommend no further action or remedial action at the project site. The objectives and
approach used to complete this report are described in greater detail in Sections 1.2 and 1.3.
The Bolsa Chica Lowlands are located in Orange County, California, (Figure 1-1) and
comprise about 1,200 acres of estuarine/marine and upland habitat. The Lowlands lie east of
the Pacific Coast Highway, between the higher elevation Bolsa Chica Mesa to the northwest
and Huntington Mesa to the east-southeast. Historically, the site and adjacent areas have been
used for agriculture, cattle grazing, as a wildlife refuge, and for recreational hunting and
fishing. However, since the 1920s, much of the area has been used for oil and gas exploration,
production, and processing. The earliest exploration occurred in the Edwards Thumb area
beyond the eastern tip of the Lowlands; oil operations in the Lowlands did not start until the
1940s (Klancher, 1999). The historical site activity as well as urban runoff draining into the
Lowlands has resulted in contaminating the plants and wildlife or their habitat.
The main focus of this project is to perform a baseline ERA for the Bolsa Chica Lowlands
(completed in this report) and to conduct a Confirmatory Sampling Program (CSP) (the final
phase of which will be completed after this ERA report in final). This work is being
conducted to characterize contamination within the Lowlands adequately and to help
establish clean-up criteria for portions of the property affected by previous activities,
primarily oil and gas production and urban runoff. It builds on previously available
information, including ecological and chemical characterization as well as the proposed
cleanup and restoration of the Lowlands.
The proposed restoration plan includes a mix of Full Tidal and Managed Tidal coastal
wetland habitats and non-tidal Seasonal Ponds (Figure 1-2). Once these habitats and ponds
are provided, more of the project site can eventually become a state or federal wildlife
refuge in addition to serving as mitigation for habitat losses elsewhere. Portions of the
Lowlands are currently managed as an Ecological Reserve by the California Department of
Fish and Game (including portions of Inner and Outer Bolsa Bay and the area delineated on
Figure 1-2 as “Non-tidal Portion of Ecological Reserve”). The rest of the project area is not
now managed as a wildlife refuge, but will be following site restoration.
The proposed restoration and anticipated future use of the Lowlands served as the focus of
the development of the ecological management goals for the site, which are:
• Sediment, surface water quality, and food source conditions capable of supporting
terrestrial, aquatic, and semi-aquatic plant and wildlife populations that would typically
be found in Full Tidal and Managed Tidal coastal wetland habitats, and non-tidal
Seasonal Ponds.
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SECTION 1: INTRODUCTION
• Sediment, surface water quality, and food source conditions supportive of individuals of
special-status biota and migratory birds protected under the Migratory Bird Treaty Act
likely to be found in Full Tidal and Managed Tidal coastal wetland habitats, and nontidal
Seasonal Ponds.
As part of this restoration effort, the nature and extent of contamination on the site is being
investigated and evaluated. Two important elements of the investigation include an:
• Ecological Risk Assessment (ERA) (this document) to evaluate contaminants present at
the site at concentrations that present a risk to fish, wildlife or their habitat. The ERA
identifies exposure pathways and associated site-specific assessment endpoints. The
ERA also characterizes the ecological effects of the contaminants of concern. This and
other information and analysis in the ERA has been or will be used to (among other
things): (a) assess the nature of the contamination at the site and identify the general
areas of the site that contain contamination (b) assess the nature, characteristics, and
sensitivities of the natural resources at the site (c) determine the extent to which the
contamination threatens to impact natural resources at the site and (d) identify the types
or routes of exposure to the contamination that pose an unacceptable risk; and
• Confirmatory Sampling Program (CSP) to delineate the extent of on-site contamination
and the exact bounds of needed clean-up efforts. (The CSP was not completed at the
time of publication of this report.)
Two important outcomes of the ERA are identification of (a) chemicals that will be
considered for further evaluation or remediation and (b) chemicals that need not be
considered any further. Chemicals that should be retained for further evaluation or
remediation are referred to as Chemicals of Ecological Concern (COECs) and are listed
in Tables ES-1 to ES-3.
The results of this ERA will be used as a tool used to establish clean-up criteria for portions
of the property affected by on-site contamination. It builds on previously available
information about the site (including ecological and chemical characterization, as well as
planned restoration), which was used to plan and conduct the current work.
Additionally, delineation of boundaries around the contaminated portions of the site will
be completed as part of the future activities including the development of the remediation
plan. This baseline ERA does not assess the overall areal extent of the contamination,
generate or identify remediation goals or clean-up concentrations, or identify the sensitive
habitat areas to be protected from disturbance. The development of clean-up goals is a
complex risk management process that involves an evaluation of the information contained
in the ERA and a range of other factors, such as technical feasibility and appropriate levels
of risk.
In the future, this baseline ERA will be used to evaluate the ecological impacts of alternative
remediation strategies and establish clean-up levels that will protect the natural resources at
risk. However, additional delineation of individual sites will be needed to determine the
exact bounds of the clean-up effort. The CSP results will include this type of information.
The results of the ERA will be used in the development of the CSP.
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SECTION 1: INTRODUCTION
The ERA and CSP are being conducted for the Bolsa Chica Lowlands, as described in the
original and revised Work Plans for the project (CH2M HILL, 1998a and 2000). This ERA is
the fourth in a series of reports and data deliverables. Previous reports included the Scoping
Assessment (CH2M HILL, 1998b), the sediment sampling analyses results for proposed
dredge areas that were based on a separate sampling plan (Kinnetic Laboratories/ToxScan,
Inc. and CH2M HILL, 1999), and the Ecological Effects Characterization (EEC)
(CH2M HILL, 1999), which presented the first two major components of the ERA-the
Problem Formulation and the Analysis.
1.1 Objectives and Scope
The overall objective of the ERA is to define the nature of site contamination in order to
develop site-specific, clean-up criteria and goals to protect fish and wildlife and their food
chains in the Bolsa Chica Lowlands. The overall objective of the CSP will be to define the
extent of site contamination. Two of the main tasks to accomplish this objective were to
conduct field sampling for contamination and test for toxicity or bioaccumulation of
contaminants in the Lowlands. The resulting information, which supplemented existing
data from the Lowlands, was used to:
• Aid in the Preliminary Level II Preacquisition Environmental Contamination Survey for
portions of the Bolsa Chica Lowlands where existing data are insufficient, especially for
the Fieldstone Property and Lowland Pocket areas.
• Support the ERA by providing data over wider areas of the Lowlands than has been
available and by providing the chemical and bioassay/ bioaccumulation data necessary
to assess ecological risks and determine clean-up criteria.
• Provide additional data at known or suspected contaminated sites within the Bolsa
Chica Lowlands, to determine the nature and extent of this contamination.
• Obtain supplemental physical and environmental contaminant data to aid in the design
of wetland restoration, including dredging permitting and disposal/reuse options.
The EEC Report (CH2M HILL, 1999) provided information related to these first three
purposes. The specific objectives of that report were to:
• Incorporate and update the information from the Scoping Assessment to provide the
Problem Formulation for that report and the future ERA.
• Present results of the ERA Sampling and Analyses (as described in the Work Plan and
summarized subsequently) to provide the Exposure Characterization and the Ecological
Effects Characterization for information collected onsite.
This ERA completes the process begun in the EEC Report (CH2M HILL, 1999) and, in
combination with the dredge area characterization report (Kinnetic Laboratories/ToxScan,
Inc., and CH2M HILL, 1999), fulfills all four purposes listed previously. The specific
objectives of this ERA report are to:
• Incorporate environmental data from the ERA Sampling and Analyses, the Focused
Sampling and Analyses, and relevant data from the Tetra Tech Phase II Environmental
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SECTION 1: INTRODUCTION
Assessment (1996) into a single ERA chemical database for evaluation of potential risks
to aquatic and terrestrial receptors in the Lowlands.
• Incorporate and update the information from the EEC Report to provide the Problem
Formulation, Exposure Characterization, and Ecological Effects Characterization for this
ERA.
• Present the results of the Risk Characterization, including weight of evidence for
potential risks to aquatic and terrestrial receptors as well as a summary of uncertainties
and/or limitations in the evaluations conducted.
• Present the conclusions and recommendations of the ERA.
1.2 Project Approach
The ERA was conducted using a phased approach as recommended by the U.S. EPA (1992a
and 1998) and California EPA (Cal/EPA 1996a and 1996b). This approach consisted of three
data collection or evaluation phases (Figure 1-3) that were used to produce various
documents, as described below. The data and observations from one phase were used to
determine whether further studies were necessary to meet the objectives of the ERA. This
ensured that “…only the necessary work [was] done and all of the necessary work [was]
done” (U.S. EPA, 1992c). The three data collection phases and associated reports for the
Bolsa Chica Lowlands are:
Phase 1 – Initial review of available data resulting in the CSP/ERA Work Plan (1998a) and
the Scoping Assessment (CH2M HILL, 1998b).
Phase 2 – ERA Sampling and Analyses. Collection and evaluation of additional site-specific
data and preparation of the EEC Report (CH2M HILL, 1999). The Work Plan was then
revised (CH2M HILL, 2000) to describe the next phase of sampling.
Phase 3 – Focused Sampling and Analyses. Additional collection and evaluation of sitespecific
data to fill any remaining data gaps and preparation of this final baseline ERA.
The Work Plan and Scoping Assessment (Phase 1) reviewed and evaluated previously
available data (with the Bolsa Chica Technical Committee) in sufficient detail to identify
chemicals, habitats, and receptors of concern and screen chemical concentrations against
available criteria, standards, or effect levels. The previously available data (Steffeck, et al.,
1996; Tetra Tech, 1996) focused primarily on selected sites within the Lowlands where
known or suspected oil field activities or urban inflow most likely resulted in contaminants
being introduced into the Lowlands environment. Little sampling and few analyses had
been done in most of the Bolsa Chica Lowlands.
The site wide sampling and analyses for the project were implemented in two rounds – the
ERA Sampling and Analyses (first round) and the Focused Sampling and Analyses (second
round). Because of schedule constraints for the project and the level of data review and
evaluation conducted to prepare the Work Plan, the Technical Committee determined that
the first round of sampling sampling could be conducted concurrently with preparation of
the Scoping Assessment (Figure 1-3).
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SECTION 1: INTRODUCTION
The ERA Sampling and Analyses (Figure 1-3) were designed to:
• Complete the sampling for areas away from known or suspected sources of
contamination (described as Random Sampling)
• Conduct toxicity and bioaccumulation bioassays (using site-collected sediment or water
from random and focused sites)
• Analyze field-collected biota
Samples were collected in all Cells within the Lowlands to facilitate characterizing the entire
site. Co-location of field-collected biota (e.g., plants and wildlife) and abiotic exposure
media (e.g., sediment and water) was emphasized, to the extent possible, to take the
mobility of animal species into consideration. The data also were used to establish on-site
background levels of metals (Section 3.1.1). The areas sampled for ERA purposes included
material within the dredging footprint for the Full Tidal habitat, but only for that portion
just below the depth of dredging (because that is where organisms would be exposed postrestoration).
The bioassays for the ERA were designed to determine acceptable levels of
inorganic and organic chemicals in abiotic exposure media to which ecological receptors
might be exposed under current or future conditions. Bioassay media included sediment,
pore water, and surface water from random and focused sampling sites as described in
Sections 4.2, 4.3, and 4.4 of the Work Plan (CH2M HILL, 1998a and 2000) and summarized
in Appendix A.
The second round of sampling and analyses – the Focused Sampling and Analyses
(Figure 1-3) – was designed to evaluate the nature and extent of contamination, if any,
associated with previously identified known or suspected sources (such as sumps, wells,
pipelines, maintenance areas, etc.). The focused sampling was conducted after the Scoping
Assessment and the EEC Report had been completed, and results were used in this final
baseline ERA. The findings of the ERA (especially the results from bioassays and
background levels of inorganics derived from the ERA Sampling and Analyses) will be used
to evaluate remediation needs.
This ERA consists of three major components – the Problem Formulation, the Analysis
(which includes the Exposure Characterization and the Ecological Effects Characterization),
and the Risk Characterization. The relationship of these components is shown on Figure 1-4.
The ERA followed established, scientifically sound protocols and methodologies. These
protocols and methodologies were adapted to meet the specific needs of the Bolsa Chica
project. One adaptation was the preparation of an interim report, the EEC Report
(CH2M HILL, 1999), which included the Problem Formulation and Analysis components of
the baseline ERA. This adaptation was implemented in response to recommendations from
the Technical Committee to conduct site sampling in two phases so the results of the first
phase (ERA Sampling and Analyses) could be evaluated to determine the most effective
approaches for conducting the second phase (Focused Sampling and Analyses) at known or
suspected sources of contamination. It was expected that reductions in the suites of analytes
(because particular analytes were not found to be of concern in the Ecological Effects
Characterization), using higher detection limits (because they would be sufficient to detect
levels of concern), and implementing other strategies (such as evaluating correlations
among chemicals) could be used to lower the costs for focused sampling and analyses.
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SECTION 1: INTRODUCTION
Based on that recommendation, a programmatic decision was made to defer the Risk
Characterization (and completion of the ERA) until the focused sampling and analyses
were completed.
This ERA identifies risk to ecological receptors by comprehensively evaluating existing
information and data (as appropriate) as well as new data developed through the focused
sampling and analyses. The assumptions and ecological endpoints outlined for the ERA are
based on the ecological management goals for the site, which will become a state or federal
refuge and will serve as mitigation of habitat losses elsewhere. Additional site delineation
will be necessary once the ERA results are evaluated and clean-up goals are developed.
1.3 Guidance
The ERA was performed, according to the following guidance documents and work plans:
• Guidance for Ecological Risk Assessment at Hazardous Waste Sites and Permitted
Facilities (Cal/EPA, 1996a and 1996b)
• Framework for Ecological Risk Assessment (U.S. EPA, 1992a)
• ECO Updates, Volume 1, Numbers 1 through 5 (U.S. EPA, 1991a, 1991b, 1992b, 1992c,
and 1992d)
• ECO Updates, Volume 2, Numbers 1 through 4 (U.S. EPA, 1994a, 1994b, 1994c, and
1994d)
• ECO Updates, Volume 3, Numbers 1 and 2 (U.S. EPA, 1996a and 1996b)
• Guidelines for Ecological Risk Assessment (U.S. EPA, 1998)
• Work Plan for Confirmatory Sampling and Ecological Risk Assessment for Bolsa Chica
Lowlands Project, Huntington Beach, California (CH2M HILL, 1998a and 2000)
1.4 Assumptions
The ERA was conducted under the following major assumptions or constraints:
• No additional remedial actions will be taken (i.e., the ERA will evaluate baseline
conditions at the time sampling was conducted).
• The media of primary ecological concern for terrestrial and semi-aquatic receptors were
soil, surface water, and biota (for secondary consumers). However, because many
portions of the site are seasonally flooded, soil and sediment were considered
synonymously.
• The media of primary ecological concern for aquatic receptors were sediment and
surface water.
• Chemicals for which analyses were not performed were not evaluated.
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SECTION 1: INTRODUCTION
• Chemicals not detected in some samples were assumed present in those samples at half
their sample-specific reporting limit, if they were detected at least once within a defined
evaluation area.
• Chemicals not detected in any sample collected for a given medium (e.g., sediment)
were assumed not present.
• The exposure point concentration was considered the concentration of each chemical in
a specific exposure medium that represents the maximum reasonable exposure for each
biological receptor. This value was used to estimate potential risks to a specific receptor
through comparison to effect levels developed from site-specific bioassays and literature
information.
• The exposure point concentrations for immobile or relatively sedentary receptors (aquatic
and terrestrial plants and invertebrates) were the observed maximum concentrations for
chemicals detected in each evaluation area.
• The exposure point concentrations for receptors with limited movement in the Lowlands
(fish) were the observed maximum concentrations detected in each evaluation area. This
selection was based on the physical limitations to their mobility (because they are unable
to move between cells) and the limited availability of surface water data. (For most
analytes, sufficient data were not available to calculate a 95-percent upper confidence
level [UCL] of the mean.)
• The exposure point concentrations for mobile receptors (birds and mammals) were the
95-percent UCL of the mean for chemicals detected in the exposure area, unless the 95-
percent UCL exceeded the maximum detected concentration, in which case the
maximum detected concentration was the exposure point concentration.
• The exposure point concentration for each chemical is as bioavailable as the chemical on
which the toxicity information is based.
• The toxicological information used represents site-specific bioassay results in
combination with information available from literature and database searches.
• The primary exposure pathways for aquatic organisms are ingestion and direct contact
with sediment and surface water.
• The primary exposure pathways for semi-aquatic and terrestrial organisms are direct
contact with soil (plants); direct contact and ingestion of soil (invertebrates); and
ingestion of sediment/soil, surface water, and food (birds and mammals). (Direct
contact and inhalation exposures were not quantitatively evaluated for birds and
mammals. The contribution of these pathways to the overall risk is expected to be minor
in comparison to other pathways evaluated, and available dermal and inhalation
toxicological information is limited.)
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SECTION 1: INTRODUCTION
1.5 Organization of the ERA Report
This ERA is organized as follows:
• Section 2.0 – Problem Formulation. Provides information, largely taken from the
Scoping Assessment (CH2M HILL, 1998b) and updated in the Ecological Effects
Characterization (CH2M HILL, 1999), that was used to develop the exposure and
ecological effects characterizations in the Analysis section. This section presents
preliminary site background information; describes the different habitats found onsite;
lists potential ecological receptors for the site; summarizes chemicals of potential
ecological concern (COPECs), screening reference toxicity values (RTVs) for the
COPECs, and results of screening for potential risks that was conducted in the Scoping
Assessment; lists assessment endpoints, risk hypotheses, and measures that will be used
to assess ecological effects; and presents the ecological conceptual site model for
potential ecological exposures for representative ecological receptors.
• Section 3.0 – Analysis. Presents the Exposure Characterization and Ecological Effects
Characterization, which analyze and evaluate results of the two phases of field sampling
(the ERA Sampling and Analyses and the Focused Sampling and Analysis), as well as
relevant data from Tetra Tech (1996). This section summarizes the field sampling and
analysis; presents the data evaluation for chemicals detected in the Lowlands; presents an
updated evaluation of background concentrations of inorganics detected onsite;
summarizes potential sources of chemical stressors and their spatial distribution across the
site; summarizes chemical-specific exposure point concentrations of COPECs to which
plants and animals may be exposed; presents estimated daily doses for terrestrial and
semi-aquatic birds and terrestrial mammals; reports the results of bioassays performed on
sediment, pore water, and surface water from the site; discusses dose-response
evaluations conducted using univariate regression analyses; and summarizes the exposure
and effects information into an exposure profile and stressor-response profile.
• Section 4.0 – Risk Characterization. Presents results of quantitative and qualitative risk
evaluations to provide a weight-of-evidence for characterizing the presence or absence
of risk to representative receptors in each evaluation area of the Lowlands. This section
also includes a discussion of uncertainties and limitations associated with the
information and methodologies used in this ERA.
• Section 5.0 – Conclusions and Recommendations. Provides a summary of conclusions
of the ERA and recommendations for the site as a whole, as well as specific evaluation
areas within the Lowlands.
• Section 6.0 – References. Provides a list of information sources used in this report.
• Tables, Figures, and Appendices. Contain information used to support ERA
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SECTION 2
Problem Formulation
The Problem Formulation presents and evaluates information that will be used to develop
and focus the Analysis component of the ERA. Much of the information presented in this
section was taken from the Scoping Assessment (CH2M HILL, 1998b) and the Ecological
Effects Characterization (CH2M HILL, 1999). The end product of the Problem Formulation
is an ecological conceptual site model that describes potential ecological receptors (plant
and animal species) that may be affected at the site, COPECs, important site aspects to be
protected (referred to as assessment endpoints), and means by which the assessment
endpoints will be evaluated (called measures). The information used to develop the
ecological conceptual site model includes the following:
• Site Background – provides a description of the physical setting, climate, historical
activity at the site, and previous site investigations that have been conducted.
• Ecological Characterization – provides a description of the ecological setting, including
identification of habitats and potential ecological receptors.
• Chemicals of Potential Ecological Concern – provides a description of the preliminary
identification of COPECs based on the previous Tetra Tech (1996) sampling efforts,
including preliminary evaluations of data usability, background concentrations, and
comparisons of preliminary data to screening effect levels to identify COPECs.
• Assessment Endpoints and Measures – provides a description of the development of
assessment endpoints (important aspects of the site to be protected), risk hypotheses
(statements of how potential exposure to stressors could occur at the site), and measures
(predictors of assessment endpoints and the means by which the risk hypotheses will be
evaluated).
2.1 Site Background
This section describes physical characteristics of the site including location and climate,
provides a review of the relevant site history, and summarizes previous investigations
conducted at the site.
2.1.1 Location/Setting
The physical setting of the Lowlands and surrounding area was described by Jones and
Stokes (1995), OCEMA (1996), and Tetra Tech (1996), and the relevant portions of those
descriptions are summarized here. Figure 1-1 shows the location of the Bolsa Chica Lowlands
study site relative to adjacent, interconnected, marine/estuarine habitat at Huntington
Harbor and Seal Beach National Wildlife Refuge (NWR). The Lowlands project area includes
about 880 acres of terrestrial and wetland habitat recently acquired from the Koll Real Estate
Group, 306 acres in the Bolsa Chica Ecological Reserve, and about 25 acres of Southern
California Metropolitan Water District (MWD) property. Extensive and highly urbanized
watersheds drain into these three closely linked marine/estuarine systems.
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The Lowlands lie east of the Pacific Coast Highway, between the higher elevation Bolsa
Chica Mesa to the northwest and “Edwards Thumb” and Huntington Mesa to the eastsoutheast.
Surface topography is subdivided into several general areas (e.g., Pocket Area,
Fieldstone Property, Bolsa Chica Ecological Reserve, and the large central portion of the
Lowlands), but the entire study area has relatively little topographic relief. For sampling
purposes, the most important surface features (other than the general area designations and
their priorities) are the network of levees and roads that divide the Lowlands into
approximately 60 Cells. These Cells, along with surface water bodies and drainage
pathways, provide the topographic focus for the ERA.
Residential areas exist to the northeast of the Lowlands, between the upland/mesa areas to
the north (Bolsa Mesa) and east-southeast (Edwards Thumb and Huntington Mesa), and on
the upland/mesa areas themselves. Within the Lowlands, the primary land use is oil field
operation (including onsite wells throughout the site and the Whipstock area, with
wellheads for some wells that extend offshore).
The Ecological Reserve is partially accessible to the public through a boardwalk; entry is
from an access point (with a parking area) along Pacific Coast Highway. Beaches along
Pacific Coast Highway opposite the Lowlands are within the Huntington State Beach and
are used for surfing, swimming, and other recreational purposes.
2.1.2 Climate
The climate of the project area is characterized by warm, dry summers, tempered by ocean
breezes, with mild winters. The annual average rainfall of about 12 inches occurs primarily
between November and April. Fog and low clouds typically occur from February to April.
In summer, morning fog and low clouds usually persist until mid-afternoon, keeping
summer temperatures mild. The average daily temperature in the summer is 18 degrees
Celsius (C), winter temperatures average 11 degrees C, and annual temperatures range from
1.7 to 38 degrees C. The prevailing winds, which blow onshore from the southwest, help
lower summer temperatures and dissipate the summer fog. In autumn, strong, gusty winds
from the inland deserts, known locally as Santa Ana winds, cause unseasonably warm days.
2.1.3 Site History
During the late 19th and early 20th centuries, agricultural use of uplands north and east of
the site may have included livestock grazing and crop farming that might have involved the
use of fertilizers and some kinds of insecticides (Jones and Stokes, 1995; OCEMA, 1996).
Many of these agricultural areas drained into the Lowlands, and runoff may have contained
certain metals and pesticides. Some of the metals are related to the application of pesticides
or herbicides or to repeated irrigation and runoff cycles.
In the 1890s, the Bolsa Chica Gun Club used the Lowlands as a wildlife preserve for
recreational hunting and fishing. Recreational hunting by Bolsa Chica Gun Club members
ended in 1964 (Jones and Stokes, 1995; OCEMA, 1996). One of the events that has most
profoundly affected water quality was the construction of tide gates between Inner and
Outer Bolsa Bay by the Bolsa Chica Gun Club in 1899. With the resulting reduction in the
tidal prism, the natural opening at Los Patos (now Warner Avenue) between Bolsa Bay and
the Pacific Ocean silted in. A new opening that connected Outer Bolsa Bay to Sunset Bay
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SECTION 2: PROBLEM FORMULATION
(now Huntington Harbour) was cut through Bolsa Chica Mesa. Construction of berms and
dikes to enhance duck habitat (e.g., create freshwater habitat) may have resulted in
increased evapoconcentration cycles (metals, minerals, salinity from fresh, brackish, and
seawaters) in the shallower soils as waters came into the Lowlands and then slowly
evaporated during the dry season. However, the degree to which evapoconcentration may
have been impacted by construction activities has not been well documented.
Since 1920, the site and surrounding area have been used for oil and gas exploration,
production, and processing as part of the Huntington Beach Oil Field. The earliest
exploration occurred in the Edwards Thumb area at the eastern tip of the Lowlands. Oil
operations in the Lowlands did not start until the 1940s (Klancher, 1999).
An examination of aerial photographs from 1938 and 1947 indicates drainage from surrounding
areas entered the site at several locations. Discrete channels entered areas that are now
designated as Cell 63 (Freeman Creek) and Cell 66. Freeman Creek drainage would have
flowed westward through channels that are now parts of Cells 30, 18, 17, and 5 into Inner Bolsa
Bay. Drainage entering through Cell 66 would have flowed to the area that is now Cell 67.
A more generalized drainage pattern to the Lowlands appears to have existed northwest of
the area, where the Garden Grove-Wintersburg Flood Control Channel (which drains to
Outer Bolsa Bay) was subsequently constructed. Another generalized drainage pathway
(without a defined channel) appears to have entered the Lowlands from oilfield
developments east of the site. This drainage pathway would have entered the Lowlands
through what is now Cell 36.
More than 430 oil wells are on the site, including many that have been abandoned. Active
and inactive oil wells are present, primarily on earthen pads elevated several feet above the
natural grade of the Lowlands. Most of the wells are characterized by aboveground pumps
and below-grade cellars. Open, unlined sumps within the Lowlands area have been used
historically to process or dispose of oilfield wastes, including drilling muds, oil/water
separation wastes, brine, and other oily waste.
An extensive network of active, inactive, and abandoned oil and gas pipelines criss-cross the
site along the elevated oil roads. Most of the main transmission pipelines are aboveground
in the Lowlands area, except for shorter pipelines from individual wells to the main
transmission lines, which are sometimes underground. Two gas lines that carry petroleum
products from offsite locations traverse the site.
Three tank farms (the North Bolsa Tank Farm, the South Bolsa Tank Farm, and the State Lease
Tank Farm) and related structures and equipment yards were formerly present in the project
area. The tank farms, which were at the eastern side of the project area, have been removed.
Soil contamination has been associated with each of the tank farms (Steffeck, et al., 1996).
Until recently, a gas plant operated on the Huntington Beach Mesa adjacent to the eastern
edge of the property. The gas plant processed condensate from onsite and offsite production.
Contamination by condensate has been detected in the soil beneath the old gas plant.
Ancillary operations to petroleum production include an outdoor sand blasting and spray
painting area on the eastern Lowlands. A helipad is on the Huntington Beach Mesa (outside
the property boundary); an underground jet fuel tank and underground waste tank are
associated with the helipad (OCEMA, 1994).
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SECTION 2:PROBLEM FORMULATION
The entire interconnected marine/estuarine complex of Seal Beach NWR, Huntington
Harbour, and Bolsa Chica Lowlands (1,400 to 1,900 acres) receives stormwater runoff and
urban drainage from a total watershed area of approximately 48,000 to 50,000 acres
(Figure 1-1). Almost 18,000 acres of this watershed drain directly to the Garden Grove-
Wintersburg Flood Control Channel. The Lowlands also receive nonpoint runoff from
another 2,230 acres (CDFG/USFWS, 1976; CH2M HILL, 1994). Photos from the late 1940s
show drainage pathways bisecting the Lowlands from the east and southeast, draining into
Inner Bolsa Bay. The volume of urban runoff draining into the Lowlands has increased in
the last 5 years from several new residential developments in the uplands. Nutrients and
various contaminants—heavy metals, organophosphate pesticides, and organochlorine
herbicides—reaching the Lowlands from several of these sources are documented by Tetra
Tech (1996), and some of their probable impacts are described in Macdonald, et al. (1992).
Title to the Lowlands was transferred to the California State Lands Commission in February
1997. Funding by the Port of Los Angeles and Port of Long Beach will be used to construct a
new ocean inlet channel and subtidal basin that will be used to restore part of the existing
non-tidal wetlands ecosystem to Full Tidal condition (shown conceptually on Figure 1-2).
Development of these proposed restoration features will be overseen by the eight federal
and state agencies that have worked together to make the Bolsa Chica acquisition possible.
Full restoration of the Lowlands is planned to take place over 15 to 20 years. According to a
recent conceptual proposed restoration plan (Figure 1-2), while the Full Tidal, Managed
Tidal, and Seasonal Ponds habitats will be restored relatively soon, it may be 15 years or
more before the Future Full Tidal and Whipstock areas are restored. Construction phasing
for the proposed habitat restoration will, of course, involve the orderly consolidation and
ultimate removal of active oil field operations.
2.1.4 Previous Investigations
The Bolsa Chica Lowlands have a long history of potential contamination, hazardous waste
investigations, and site clean-up actions. Historical contaminant sources include lead shot
from Bolsa Chica Gun Club activities (1890-1964), but most contamination has come from
early operation and expansion of the Huntington Beach Oil Field (1920 to the present) and
from urban runoff and stormwater flows (i.e., Garden Grove-Wintersburg Flood Control
Channel, Springdale Pump Station, and Seacliff runoff) that have been diverted onto the site
(1940s to the present).
Several hazardous waste site contamination investigations have been conducted across
portions of the Lowlands and adjacent mesas (Figure 2-1), including the following:
• Woodward Clyde (1987)
• Groundwater Technology (1989)
• Earth Technology (1987, 1988, 1990)
• Schaefer Dixon Associates (1991)
• Tetra Tech (1996)
Key areas of concern in the Lowlands from the Schaefer Dixon Phase I Environmental
Assessment (1991) are shown on Figure 2-1. The principal non-aquatic areas of concern
more recently sampled during the Tetra Tech (1996) Phase II investigation are shown on
Figure 2-2, and Figure 2-3 shows sites with confirmed contamination.
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SECTION 2: PROBLEM FORMULATION
Numerous clean-up actions have occurred over the past two decades. While no formal
remediation was performed when the State Ecological Reserve was created and partially
diked (1977 to 1978), visibly contaminated soils and debris were scraped off the Reserve
areas and removed. Cleaner, but probably untested, in situ soils were used to build the
dikes around the Reserve.
Extensive remediation associated with the active oil field “waste handling facility” was
carried out in the 1980s and 1990s. More recently CalResources, now AERA Energy, working
with Signal Landmark/Koll, has remediated decommissioned oil wells, pipelines, and oil
field facilities, such as the former tank farms and gas plant, as well as accidental spills.
Under the terms of the site purchase and proposed habitat restoration agreement
(Memorandum of Agreement, October 1996, Amended December 1996 and February 1997),
portions of the Lowlands will continue to be operated by AERA Energy as an active oilfield.
If sufficient funds are available to buy out producing wells or as the wells are phased out,
closed down, and cleaned up, these active oilfield areas will also be restored fully to coastal
wetland habitats.
2.2 Ecological Characterization
Bolsa Chica is classified as a bay estuary having deepwater habitats with extensive intertidal
wetlands (Ferren, 1990; OCEMA, 1996). The Bolsa Chica Wetlands are the remnant of what
was once a vast saltwater and freshwater wetlands complex in the historic floodplain of the
Santa Ana River. The generally open and broad mouth of the bay allowed marine water to
flood the adjacent marshes at low elevation during high tide. During the winter wet season,
rainfall and streamflow dilute the marine waters; during the rest of the year, ocean water
dominates.
2.2.1 Identification of Habitats
The Lowlands include habitats that at one time supported salt marsh, brackish marsh,
freshwater marsh, open water, mudflats, dunes, and sandy flats. The present condition of
these lowland habitats has been altered and degraded by development that has removed
much of the site from tidal influence. These alterations include dike construction, road and
pad construction for oil development, and channel construction for flood control. Removal
from tidal influence has adversely affected much of the salt marsh habitat, which is now
mostly degraded or ruderal habitat (i.e., weedy species tolerant of poor soils, including
mustard, ice plant, and telegraph weed).
Habitat types found in the Lowlands are briefly described in text and are shown on Figure 2-4.
2.2.1.1 Pickleweed
Saline tidal and non-tidal areas with adequate soil moisture are dominated by pickleweed
(Salicornia virginica). Other species associated with the pickleweed salt marsh habitat include
alkali heath (Frankenia salina), saltgrass (Distichlis spicata), and annual pickleweed (Salicornia
bigelovii). In non-tidal areas, ice plant (Carpobrotus edulis) is often co-dominant.
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SECTION 2:PROBLEM FORMULATION
2.2.1.2 Brackish Marsh
Areas of fluctuating or moderate salinity typically support both salt marsh and freshwater
species. Sedges (Carex spp.) and bulrushes (Scirpus spp.) are found in the brackish marshes
at the Lowlands. Brackish marshes, a small component of the Lowlands, are found in
scattered areas mostly along the perimeter of Inner Bolsa Bay as well as at the former gas
plant ponds/sumps and Freeman Creek.
2.2.1.3 Saltgrass
Dry, high saline sites are dominated by saltgrass often associated with pickleweed. Saltgrass
habitat is found near the former North Bolsa Tank Farm (NBTF) and Rabbit Island.
2.2.1.4 Tidal and Non-Tidal Open Water
Unvegetated areas of tidal water include the Inner Bolsa Bay, and unvegetated areas of
non-tidal water include channels and ponded water not created by tidal changes (mostly
on the east), such as the pond in Cell 38 and the unnamed drainage downgradient from the
golf course.
2.2.1.5 Tidal and Non-Tidal Mudflats
Tidal and non-tidal mudflats are unvegetated areas that have been covered by water for
long periods. Tidal mudflats are periodically exposed during low tide. Non-tidal mudflats
appear during summer and fall, when water levels recede and expose the bottoms of
seasonal ponds and edges of perennial ponds. Tidal mudflats provide higher quality
foraging habitat than do non-tidal mudflats.
2.2.1.6 Upland
Upland habitats at the Lowlands include areas of ruderal vegetation; coastal scrub habitat
dominated by coyote brush (Baccharis pilularis), California sagebrush (Artemesia californicus),
and saltbush (Atriplex sp.); and dunes and sandy flats that support sparse low herbaceous
vegetation species. Ruderal habitat is found along road berms, by oil pads, and adjacent to
buildings. Coastal scrub habitat is found along the bluffs of Bolsa Chica Mesa and on Rabbit
Island (Jones and Stokes, 1995).
2.2.2 Identification of Potential Ecological Receptors
The following sections summarize occurring animal species identified in the terrestrial and
aquatic habitats on the Lowlands. A detailed species list can be found in Table 2-1.
2.2.2.1 Species Observed or Expected to Occur
A list of species potentially found at the Lowlands was generated from the California
Wildlife Habitats Relationship Database System (WHR) (California Department of Fish and
Game [CDFG], 1998) (Table 2-1). This list was tailored to the Lowlands using professional
judgment and knowledge of the species. An information system created through multiagency
cooperation and maintained by CDFG, the WHR’s database components are used to
assess terrestrial vertebrate species occurrence, habitat requirements, life history information,
and relative abundance. Each species was cross-referenced with information collected during
site visits and reviews of published and unpublished data (CDFG, 1998; USACE, 1995) to
determine the accuracy of habitat associations, geographic distributions, and listing status.
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SECTION 2: PROBLEM FORMULATION
Pickleweed salt marsh has a high value for wildlife because of the density and structure of
the vegetation. Nesting and foraging marsh birds as well as Belding's savannah sparrow
(Passerculus sandwichensis beldingi) and common wildlife species, such as the great egret
(Ardea albus), great blue heron (Ardea herodias), sora rail (Porzana carolina), northern harrier
(Circus cyaneus), barn owl (Tyto alba), western harvest mouse (Reithrodontomys megalotis),
southern California salt marsh shrew (Sorex ornatus salicornicus), and western rattlesnake
(Crotalus viridis), are found in this habitat.
Brackish marsh provides nesting and foraging habitat for many wetland species. Wildlife
found in brackish marsh habitats at the Lowlands include the American bittern (Botaurus
lentiginosus), great egret, great blue heron, black-crowned night-heron (Nycticorax
nycticorax), sora rail, American coot (Fulica americana), common moorhen (Gallinula
chloropus), American kestrel (Falco sparverius), northern harrier, red-winged blackbird
(Agelaius phoeniceus), and salt marsh shrew.
Saltgrass provides low- to moderate-quality habitat for wildlife species at the Lowlands.
Species observed using this habitat include the great egret, great blue heron, sora rail,
American kestrel, northern harrier, barn owl, salt marsh shrew, western harvest mouse,
house mouse (Mus musculus), coyote (Canis latrans), and red fox (Vulpes vulpes).
The open water habitats provide foraging, protection, and resting for diverse wildlife,
especially water-dependent birds, at the Lowlands. Birds found in this habitat include the
double-crested cormorant (Phalacrocorax auritus), brown pelican (Pelecanus occidentalis),
California least-tern (Sterna antillarum), blue-winged teal (Anas discors), cinnamon teal (Anas
cyanoptera), northern pintail (Anas acuta), American wigeon (Anas americana), mallard (Anas
platyrhynchos), northern shoveler (Anas clypeata), bufflehead (Bucephala albeola), ruddy duck
(Oxyura jamaicensis), greater scaup (Aythya marila), lesser scaup (Aythya affinis), and
American coot. These birds forage on aquatic plants, invertebrates, and fish, and during the
breeding season, some may nest in adjacent upland areas.
Mudflats are used by shorebirds and wading birds, such as the American avocet
(Recurvirostra americana), black-necked stilt (Himantopus mexicanus), semipalmated plover
(Charadrius semipalmatus), snowy plover (Charadrius alexandrinus), killdeer (Charadrius
vociferus), greater yellowlegs (Tringa melanoleuca), willet (Catoptrophorus semipalmatus), and
least sandpiper (Calidris minutilla). Gulls (Larus spp.), terns (Sterna spp.), and coots also roost
and forage on non-tidal mudflats.
Coastal scrub habitat is sparse and highly degraded at the site, but it can support specialstatus
plant species. Terrestrial wildlife found in ruderal and coastal scrub habitats at the
Lowlands include the red-tailed hawk (Buteo jamaicensis), American kestrel, white-tailed kite
(Elanus leucurus), great horned owl (Bubo virginianus), mourning dove (Zenaida macroura),
rock dove (Columba livia), American crow (Corvus brachyrhynchos), northern mockingbird
(Mimus polyglottos), European starling (Sturnus vulgaris), western meadowlark (Sturnella
neglecta), house finch (Carpodacus mexicanus), house sparrow (Passer domesticus), western
harvest mouse, house mouse, coyote, and red fox.
Dunes and sandy flats at the Lowlands are found mostly on islands and provide
good-quality nesting and roosting habitat for shorebirds and seabirds. Birds using the dunes
and sandy flats include the Caspian tern (Sterna caspia), elegant tern (Sterna elegans), Forster's
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SECTION 2:PROBLEM FORMULATION
tern (Sterna forsteri), California least tern, western snowy plover, killdeer, and black
skimmer (Rynchops niger).
2.2.2.2 Special-Status Species
The California Natural Diversity Database (CNDDB) (RareFind, 1999) was used to identify
special-status plant and animal species and natural community types for which records of
occurrence exist on or within a 5-mile radius of the project area. Data included in the
CNDDB, which is maintained by the CDFG, are compiled by opportunistic rather than
systematic means and, therefore, may not include all records of species occurrences and
habitats for a given area. As with the list of species expected to occur onsite, each specialstatus
species was cross-referenced with information collected during site visits and reviews
of published and unpublished data (CDFG, 1998; USFWS, 1990; USACE, 1995) to determine
the accuracy of habitat associations, geographic distributions, and listing status. A list of
special-status species potentially occurring in the Bolsa Chica Lowlands is in Table 2-2.
2.3 Chemicals of Potential Ecological Concern
This section describes selection and preliminary evaluation of COPECs. The COPECs were
selected as part of the Scoping Assessment (CH2M HILL, 1998b) through evaluation of
existing data and comparison to available background concentrations and screening-level
benchmarks, as described in the following subsections. The COPECs selected in the Scoping
Assessment were used to:
• Ensure that field activities detailed in the Work Plan (CH2M HILL, 1998a) would yield
data sufficient to fully characterize the potential risk to ecological receptors from siterelated
contaminants and activities
• Provide the basis for evaluations conducted in the EEC Report and this ERA
The ERA was completed using analytical results from the Phase II environmental
investigation (Tetra Tech, 1996) and the ERA Sampling and Analyses and Focused Sampling
and Analyses (CH2M HILL, 1998a; and 2000). Other previous investigations (Woodward
Clyde, 1987; Groundwater Technology, 1989; Earth Technology, 1987, 1988, 1990; and
Schaefer Dixon Associates, 1991) were considered to the extent that they are still relevant.
The data from sampling conducted by Tetra Tech (1996), as well as that conducted through
the CSP/ERA (CH2M HILL, 1998a and 2000) were compiled into a single ERA chemical
database. The data evaluation for the ERA is presented in Section 3. Those data meeting
data quality parameters were used to quantitatively and qualitatively evaluate the potential
ecological risks from chemical concentrations in soil, sediment, surface water, and biota.
Final chemicals of ecological concern (COECs) have been identified based on these
evaluations, as described in Sections 3 and 4.
2.3.1 Preliminary Data Evaluation
A list of sitewide COPECs was compiled by the Bolsa Chica Technical Committee prior to
preparation of the Work Plan and the Scoping Assessment (Table 2-3). This list was
expanded in the Scoping Assessment to include all chemicals detected in soils, sediments,
surface water, and biota (benthic infauna, fish, terrestrial plants, and terrestrial mammals)
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SECTION 2: PROBLEM FORMULATION
during the Phase II environmental sampling conducted by Tetra Tech (1996) as well as those
chemicals identified by the Technical Committee (Table 2-4). The chemicals identified by the
Technical Committee were based on the results of the Tetra Tech Phase II sampling, with
data interpretations by the U.S. Fish and Wildlife Service (USFWS) and CDFG (Steffeck,
et al., 1996).
Analytical data from the Tetra Tech sampling effort (Tetra Tech, 1996; Steffeck, et al., 1996)
were evaluated to confirm that they met certain data quality requirements, and data were
retained or eliminated from further evaluations using the following guidelines:
• Chemical results with laboratory or validation qualifiers of any letter except “U,” “UJ” or
“ND” (nondetected) were considered detected and were retained for further screening.
• Chemical results with laboratory or validation qualifier “U,” “UJ,” or “ND” were
considered nondetect and were evaluated at one-half the reported value in further
screening if the chemical was detected at least once at the site.
• Chemical results with laboratory or validation qualifier “R” were considered rejected
and were removed from further screening.
• The maximum detected value for samples collected in each area was retained as the
exposure point concentration for screening purposes.
Chemical data for each medium meeting these requirements were retained for further
evaluation in the Scoping Assessment. The range of detected concentrations in each area
are presented for soil (Table 2-5), sediment (Table 2-6), surface water (Table 2-7), benthic
infaunal tissue (Table 2-8), fish tissue (Table 2-9), terrestrial plants (Table 2-10), and
terrestrial mammals (Table 2-11). The raw data used for this evaluation are presented
in Appendix A of the Scoping Assessment (CH2M HILL, 1998b) and are included in
Appendix D. Groundwater and biota data were not evaluated in the Scoping Assessment,
but they were used where appropriate in the assessments conducted as part of the
Ecological Effects Characterization and ERA.
2.3.2 Preliminary Background Evaluation
Many inorganic chemicals occur naturally, and ecosystems evolve around these naturally
occurring levels. Therefore, inorganic chemicals detected at concentrations below local
background levels are typically not considered a threat to ecological receptors and are
generally eliminated from further screening processes. In addition, some inorganic chemicals
that occur naturally are not of concern because of their ubiquitous nature. These elements
(i.e., calcium, magnesium, potassium, and sodium) have low toxicities for terrestrial and
aquatic organisms and act as macronutrients for natural systems. Therefore, these elements
were not assessed as COPECs. For the purpose of this report, the source of all organic
chemicals detected was assumed to be anthropogenic, and background screening was not
conducted for organic chemicals.
Background evaluations were conducted as part of the ongoing ERA investigations
(Section 3.1.3) because the Phase II environmental sampling conducted by Tetra Tech (1996)
did not include any sampling to specifically address background levels for inorganic
constituents. To temporarily address the lack of site-specific soil samples for preliminary
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background evaluations, Steffeck, et al. (1996), recommended the use of three samples from
the oil well sites that were collected 8 feet below ground surface (bgs) in an area with an
estimated 6 feet of fill (OW3, OW12, and OW13). It was assumed that these three samples
were not impacted by site activities (i.e., they lacked organic compound contamination) and
that they were representative of soil conditions within 2 feet of the “pre-filled” ground
surface. The results of the inorganic analyses for these three samples were averaged to
estimate preliminary background concentrations for inorganic chemicals in both soils and
sediments from the Bolsa Chica Lowlands (Table 2-12). The preliminary background values
were used for both soil and sediments, because most of the site will be flooded after
remediation. No background values were available for surface water.
Because of the limitations of this background evaluation and the ongoing sampling, results
of background comparisons for inorganic chemicals were not used as the basis for removing
a given chemical from the list of COPECs for the ERA.
2.3.3 Preliminary Evaluation of Chemical Contamination
The preliminary evaluation of chemical contamination during the Scoping Assessment
(CH2M HILL, 1998b) was limited to comparing site data to available screening benchmarks
for soil, sediment, and surface water.
Screening benchmarks for sediment and surface water were selected from available sources,
including toxicological databases, wildlife toxicological reviews, and scientific literature.
Sediment screening benchmarks were selected from U.S. EPA proposed values (U.S. EPA,
1993a, 1993b), U.S. EPA sediment quality criteria and benchmarks (U.S. EPA, 1996b), effects
range low (ER-L) values from Long et al. (1998) and Long and Morgan (1990), lowest effects
levels in the sediment toxicity database compiled by Jones et al. (1997), lowest effect levels
from the Ontario sediment quality guidelines (Persaud et al., 1993), threshold effects levels
from the Florida state sediment quality guidelines (MacDonald, 1994), and threshold effects
concentrations from the Assessment and Remediation of Contaminated Sediment Project
(Jones, et al., 1997; U.S. EPA, 1996c). In addition, sediment screening benchmarks for
nonionic organic chemicals without other available benchmarks were derived using
equilibrium partitioning methodology (Jones et al., 1997). The sediment screening
benchmarks for Bolsa Chica (Table 2-13) were selected using the following hierarchy:
• U.S. EPA values
• Lowest available marine benchmark
• Lowest available freshwater benchmark
Screening benchmarks for aquatic organism exposure to surface water were selected from
marine Ambient Water Quality Criteria (AWQC), where available, and from California
enclosed bays and estuaries proposed criteria and lowest effect levels for marine organisms
(Table 2-14). The surface water benchmark was selected using the following hierarchy:
• Chronic marine ambient water quality criteria
• California enclosed bays and estuaries proposed chronic criteria
• Chronic lowest observed effect level
When a chronic value was not available, but an acute criterion was, the acute value was
divided by an acute-to-chronic factor of 10 to estimate a chronic value.
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SECTION 2: PROBLEM FORMULATION
The available screening benchmarks used to evaluate preliminary data in the Scoping
Assessment are presented in Table 2-12 (preliminary soil background concentrations),
Table 2-13 (sediment screening benchmarks), and Table 2-14 (surface water screening
benchmarks). These benchmarks were updated in EEC Report and, again, as necessary for
this ERA. Preliminary soil background values were discussed in the previous section.
The screening process used for this phase of the evaluation was limited to comparing the
maximum concentrations of chemicals detected in soil, sediment, and surface water that
were retained in the data evaluation process (Section 2.3.1) to the selected screening
benchmarks (Tables 2-9, 2-13, and 2-14).
The maximum detected soil concentration in each area or site activity (e.g., waste sumps,
pipelines, or service roads) was screened against the preliminary background
concentrations for inorganic chemicals and the identified sediment screening benchmarks
(Table 2-15). Soils were screened against sediment benchmarks because most of the site soils
will become flooded as a result of proposed site restoration activities. Chemicals that
exceeded either background values or the sediment screening benchmarks were identified
as COPECs for the ERA. Chemicals that did not have an available benchmark were also
retained for further evaluation in the ERA.
The maximum detected sediment concentration in each area was screened against
preliminary background values and sediment benchmarks (Table 2-16). Chemicals that
exceeded either background values or the sediment screening benchmarks were identified
as COPECs for the ERA. Chemicals that did not have an available benchmark were also
retained for further evaluation in the ERA.
The maximum detected surface water concentration in each area or site activity was
screened against the selected surface water benchmark for chronic exposure (Table 2-17).
Chemicals that exceeded the surface water screening benchmark were identified as COPECs
for the ERA. Chemicals that did not have an available benchmark were also retained for
further evaluation in the ERA.
The COPECs identified in the Scoping Assessment (CH2M HILL, 1998b) for further
evaluation are presented by area for soil (Table 2-18), sediment (Table 2-19), and surface
water (Table 2-20). These COPECs, along with any others identified based on the ERA and
focused sampling efforts, were further evaluated in this ERA (Section 3).
2.4 Assessment Endpoints and Measures
The overall objective of the Problem Formulation is to describe ecological characteristics
of the Bolsa Chica Lowlands, summarize previously existing data, compare contaminant
concentrations to readily available screening benchmarks, and thereby assess whether
ecological risks may exist. To meet this objective, potential ecological effects of the site
contaminants important to decision making must be identified. Assessment endpoints
and measures relevant to ecological resources in the Lowlands are defined in this section.
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SECTION 2:PROBLEM FORMULATION
2.4.1 Assessment Endpoints
Assessment endpoints, which represent key objectives for ecosystem protection at a site, are
an expression of critical aspects of habitat structure and receptor viability that are important
to protect (Suter, 1993; U. S. EPA, 1998). Assessment endpoints provide a transition between
the ecological management goals and the measures used in the ERA. In addition, the
identification of assessment endpoints serves to focus the ERA and reduce uncertainty,
increasing the efficiency and cost-effectiveness of the risk assessment process. Assessment
endpoints were initially identified in the Scoping Assessment (CH2M HILL, 1998b) and
were revised based on new information gathered for the EEC Report and this ERA. These
revised assessment endpoints were selected using four principal criteria: (1) their ecological
relevance, (2) their political and societal relevance, (3) their susceptibility to known or
potential stressors at the site, and (4) whether they represent the management goals for the
site (U. S. EPA, 1998). The ecological management goals for the Bolsa Chica Lowlands are
presented in Section 1.
The assessment endpoints for the Bolsa Chica Lowlands are presented subsequently and in
Table 2-21 with their associated measures:
• Terrestrial and aquatic plants – Rates of growth, productivity, and survival; levels of
abundance; species composition; and community structure capable of maintaining
viable populations supportive of the post-proposed restoration community structures.
• Terrestrial and aquatic invertebrates – Rates of growth and survival, levels of
abundance, species composition, and community structure capable of maintaining
viable populations supportive of the post-proposed restoration community structures.
• Fish – Rates of species survival and reproduction and levels of abundance conducive to
the maintenance of viable populations of individual species and supportive of the postproposed
restoration community structures.
• Migratory birds (species protected by the Migratory Bird Treaty Act) – Abiotic
(sediment/soil and surface water) and biotic (prey populations) conditions favorable for
health, survival, and reproduction of migratory birds.
• Mammals – Rates of species survival and reproduction and levels of abundance
conducive to the maintenance of viable species populations characteristic of expected
post-proposed restoration community structures.
• Individual special-status biota (including plants, fish, and wildlife that are considered
threatened or endangered) – Rates of survival and reproduction necessary to maintain
current populations and promote additional future recovery.
2.4.2 Risk Hypotheses
The risk hypotheses focus on the responses of the assessment endpoints when exposed to
stressors and how the exposure could occur (U. S. EPA, 1998). The relationship between
stressors and exposures was used in the Scoping Assessment (CH2M HILL, 1998b) to develop
the risk hypotheses and ecological conceptual site models for the Bolsa Chica Lowlands.
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SECTION 2: PROBLEM FORMULATION
Stressors in the Bolsa Chica Lowlands consist of chemicals that have been released from
their primary sources to the environment either directly from onsite activities or indirectly
from offsite sources via stormwater runoff. Under current conditions, ecological receptors
could contact contaminants in sediment/soil, surface water, and/or biota. Based on the
chemical stressors and potential exposure routes, the risk hypotheses for the Bolsa Chica
Lowlands are:
• Inorganic and organic chemicals associated with onsite activities are present at
concentrations potentially toxic to terrestrial and aquatic plants, invertebrates, and
vertebrates (birds, mammals, and fish).
• Inorganic and organic chemicals associated with offsite sources are being conveyed onto
the site and are present at concentrations potentially toxic to terrestrial and aquatic
plants, invertebrates, and vertebrates (birds, mammals, and fish).
• Chemicals associated with onsite and offsite source areas are potentially
bioaccumulating in forage and prey species for secondary consumers, resulting in foodchain
transfer of contaminants.
Under current conditions in the Bolsa Chica Lowlands, ecological receptors could contact
contaminants in sediment/soil, surface water, and biota. For example, terrestrial receptors
might be exposed to the contaminants by direct contact with surface soils or sediments, or
by incidentally ingesting them during activities such as feeding. Terrestrial and aquatic
receptors could be exposed to contaminants in sediment/soil or surface waters at the site
through direct contact or uptake of the water or sediment. If forage or prey species were
contaminated from site-related chemicals, their consumers (herbivores, carnivores, or
omnivores) might also become secondary receptors via food chain transfer.
2.4.3 Measures
Three categories of measures are predictive of the assessment endpoints (U.S. EPA, 1998):
measures of exposure, measures of effect, and measures of ecosystem and receptor
characteristics. Measures of exposure are used to evaluate how exposures could be occurring.
Measures of effects are used to evaluate the response of the assessment endpoints when
exposed to the stressor. Measures of ecosystem and receptor characteristics are used to
evaluate the ecosystem characteristics that could affect exposure or response to the stressor.
Measures identified for an ERA can be from one or more of these categories, depending on
the complexity of the ERA. Criteria considered in the selection of measures are as follows:
• Corresponds to or is predictive of an assessment endpoint
• Can be readily measured or evaluated
• Is appropriate to the scale of the site
• Is appropriate to the temporal dynamics
• Is appropriate to the exposure pathway
• Is associated with low natural variability
• Is minimally disruptive to ecological community and species variability
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SECTION 2:PROBLEM FORMULATION
The following measures, which are listed in greater detail in Table 2-21, were identified for
the Bolsa Chica Lowland project site:
• Measures of Exposure—Concentrations of COPECs in sediment/soil, surface water, and
field-collected biota.
• Measures of Effects—Responses of terrestrial or aquatic plants and wildlife (actual or
potential toxic effects) to COPECs in sediment/soil, surface water, and biota; responses
of bioassay organisms to COPECs in exposure media (e.g., sediment, pore water, and
surface water); potential or actual bioaccumulation of COPECs in terrestrial or aquatic
plants and wildlife.
• Measures of Ecosystem and Receptor Characteristics—Habitat quality and home range of
representative species in comparison with the size of the contaminated area at each site.
The linkages between assessment endpoints and measures are developed in the Analysis
phase of the ERA. The Analysis includes the Exposure Characterization, which results in an
exposure profile, and the Ecological Effects Characterization, which results in the stressorresponse
profile. The assessment endpoints and measures will be evaluated in more detail
during the Risk Characterization phase of the ERA.
2.5 Ecological Conceptual Site Model
The ecological conceptual site model combines information on COPECs, potential ecological
receptors, potential exposure pathways, assessment endpoints, and measures presented in
Sections 2.2, 2.3, and 2.4, providing an overall picture of site-related exposures that can
focus the remaining evaluation of COPECs in the ERA. A preliminary ecological conceptual
site model is presented in this section (Figure 2-5). The model accommodates the various
sources of chemicals, migration pathways for chemicals, potential routes of exposure, and
potential receptors at the site.
2.5.1 Identification of Representative Species
This section describes criteria used to select representative species for the Bolsa Chica
Lowlands. Representative ecological receptors were identified as the aquatic, semi-aquatic,
and terrestrial plants and wildlife most likely affected by COPECs. Representative receptors
include primary and secondary consumers that are aquatic (e.g., microinvertebrates,
macroinvertebrates, and fish), semi-aquatic (e.g., shorebirds and other birds that feed on
aquatic biota), and terrestrial (e.g., plants, soil invertebrates, upland birds, and mammals).
The potential plant and wildlife species that could represent ecological receptors were
determined through meetings with the Bolsa Chica Technical Committee, through direct
observations of plants and wildlife in the Bolsa Chica Lowlands, as well as listings of species
that are expected to occur and special-status species that may be found (as described in
Section 2.2.2). Representative species selected are from communities that are commonly
found in the different habitat types at the site. Representative species could also be specialstatus
species for which suitable habitat has been identified. The communities potentially
exposed directly or indirectly (i.e., through the food chain) to COPECs in the Bolsa Chica
Lowlands are composed of estuarine/marine plants, free-swimming and benthic
invertebrates, and fish; semi-aquatic and upland birds; and terrestrial mammals.
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SECTION 2: PROBLEM FORMULATION
Representative ecological receptors were selected from these communities to fulfill as many
of the following criteria as possible:
• Species that are known to occur or are likely to occur at the site.
• Species that relate to the assessment endpoints selected.
• Species that are likely to be maximally exposed to the COPECs.
• Sedentary species or species with a small home range.
• Species with high reproductive rates.
• Species that are known to play an integral role in the ecological community structure at
the site.
• Species that are known or likely to be especially sensitive to the COPECs, and thus are
an indication of ecological change.
• Species that are susceptible to bioaccumulation/biomagnification of COPECs from a
limited number of food items.
• Species that are representative of the foraging guild or serve as food items for higher
trophic levels.
The representative species selected for the Bolsa Chica Lowlands ERA are:
• Aquatic and semi-aquatic representative species
− Plants — aquatic grasses and forbs
− Invertebrates — benthic macroinvertebrates
− Fish — mosquitofish, topsmelt, killifish, tilapia
− Birds (semi-aquatic) — black-crowned night-heron, black-necked stilt, and least tern
• Terrestrial/upland representative species
− Plants — terrestrial grasses and forbs
− Invertebrates — insects and spiders
− Birds (upland) — American kestrel and Belding's savannah sparrow
− Mammals — western harvest mouse and coyote
Plants were selected because of their importance as habitat or forage for primary consumers.
Invertebrates were selected because of their importance as prey species for secondary
consumers. Representative vertebrate species (fish, birds, and mammals) were selected
based on their occurrence or potential occurrence onsite. Bird species selected were further
restricted to those species known to feed onsite or those observed onsite. The primary
criteria used to select vertebrate species include special-status listing, size of home range,
representativeness of trophic level or feeding guild, and potential exposure to COPECs. The
selection criteria for the representative ecological receptors are provided in Table 2-22.
Aquatic Plants – Aquatic plants (e.g., grasses and forbs) are in direct contact with
potentially contaminated sediments and surface waters. They are non-mobile and would
have high exposure to COPECs. Aquatic plants may also bioaccumulate chemicals and serve
as a direct or indirect food source for fish and semi-aquatic birds.
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SECTION 2:PROBLEM FORMULATION
Benthic Macroinvertebrates – Benthic macroinvertebrates (various species) are primary
consumers that fulfill many of the selection criteria. They would be in direct contact with
potentially contaminated sediments and surface water, and as such, they would be exposed
to COPECs. They have a relatively small range, have high reproductive rates, and serve an
integral role in the aquatic and semi-aquatic ecosystem. They serve as a primary prey item
for fishes and some semi-aquatic representative bird species (e.g., stilt). Horned snails
(Certhidea californica), mussels (Ischadium demmissum), and grass shrimp (Palaemon
macrodactylus) were collected in 1998 as part of the ERA Sampling and Analyses.
Fish – Fish are secondary or tertiary consumers and would be exposed to COPECs in surface
water and prey items. They serve as forage for a variety of higher tropic-level fish, birds
(e.g., night-herons, egrets, cormorants, and mergansers), and mammals. Mosquitofish
(Gambusia affinis), topsmelt (Atherinops affinis), killifish (Fundulus parvipinnis), and tilapia
(Tilapia zillii) were collected for tissue analyses during the 1998 ERA Sampling and Analyses.
Semi-Aquatic Birds – Semi-aquatic birds (e.g., black-crowned night-heron [Nycticorax
nycticorax] and least tern [Sterna antillarum browni]) primarily feed on species associated with
aquatic habitats. Their habit of feeding in shallow waters for fish, amphibians, crustaceans,
and insects gives them a high potential for incidental ingestion of sediment and surface
water. Black-necked stilt (Himantopus mexicanus) eggs were collected in 1998 as part of the
ERA Sampling and Analyses.
Terrestrial Plants – Terrestrial plants are in direct contact with potentially contaminated
soils and surface waters. They are non-mobile and would have high exposure to COPECs.
Plants may also bioaccumulate COPECs in the leaves and other above-ground structures.
They serve as a food source for terrestrial birds and mammals. Saltgrass (Distichlis sp.),
pickleweed (Salicornia sp.), bassia (Bassia sp.), and alkali heath (Frankenia sp.) were collected
as part of the ERA Sampling and Analyses. (However, these invertebrates were scarce at the
time of sampling, and only a few were collected.)
Terrestrial Invertebrates – Terrestrial invertebrates, such as insects and spiders, would be in
direct contact with potentially contaminated soils or may consume contaminated prey, and,
as such, they would be exposed to COPECs. They have a relatively small range, have high
reproductive rates, and serve an integral role in the upland ecosystem. They serve as
primary prey items for some upland birds and small mammals. Spiders, beetles, and
grasshoppers were collected as part of the ERA Sampling and Analyses. (However, these
invertebrates were scarce at the time of sampling, and only a few could be collected).
Upland Birds – Upland birds, such as the American kestrel (Falco sparverius) and Belding’s
savannah sparrow (Passerculus sandwichensis beldingi), are found year-round and may be
exposed to COPECs through ingestion of contaminated food items.
Mammals – Western harvest mouse (Reithrodontomys megalotis) and coyote (Canis latrans) are
fairly common and may be exposed to COPECs through ingestion of food items. Western
harvest mouse, deer mouse (Peromyscus maniculatus), and California vole (Microtus
californicus) were trapped as part of the 1998 ERA Sampling and Analyses, primarily to
evaluate exposure of their consumers.
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SECTION 2: PROBLEM FORMULATION
2.5.2 Exposure Pathway Inclusion/Exclusion
The exposure pathway inclusion/exclusion evaluation is based on information gathered
from the problem formulation (Sections 2.2, 2.3, and 2.4) and the selection of representative
species, the probable completeness of each exposure pathway, and the potential for that
pathway to be a major or minor route of exposure and risk.
A complete exposure pathway must exist for an exposure to occur. A complete exposure
pathway must have the following elements, in addition to the presence of suitable habitat
for ecological receptors:
• Contaminant source (e.g., chemicals in waste sumps, etc.)
• Mechanism for contaminant release and transport (e.g., surface dispersion)
• Exposure point (e.g., wetland Cell, creek, or soil)
• Feasible route of exposure (e.g., ingestion)
• Receptor (e.g., fish, bird, or mammal)
Contaminant sources and release mechanisms in the Bolsa Chica Lowlands consist primarily
of onsite source areas (waste sumps, pipelines, and maintenance areas) and runoff/surface
dispersion of chemicals from the onsite areas or from offsite sources (such as urban runoff).
Ecological receptors can be exposed to chemicals in soil, sediment, or surface water via direct
or secondary exposure pathways. Direct exposure pathways include ingestion, dermal
contact, root update, uptake/transport access gills, and potentially the inhalation of organic
vapors or soil particulates. Secondary exposure pathways are limited to food-chain transfer
of chemicals that bioaccumulate. Potential exposure pathways for representative species are
summarized in Table 2-23 along with the rationale for inclusion/exclusion in the quantitative
and qualitative evaluations to be conducted in the ERA.
Terrestrial and aquatic plants can absorb chemicals via root uptake from sediment/soil or
surface water. Many chemicals absorbed by plants are deposited in the leaves. In addition to
direct toxicity to the plant, chemicals that bioaccumulate within plant tissues (e.g., leaves)
may result in food chain transfer of chemicals to higher trophic-level organisms.
Terrestrial and aquatic invertebrates can absorb chemicals through their epidermis and can
accidentally or purposefully ingest sediment during feeding or burrowing. Benthic
organisms are especially prone to exposure to chemicals in sediments as some consume the
organic materials from within the sediment (e.g., chironomids). Aquatic invertebrates also
serve as a major route of food chain transfer, because they are prey for other aquatic
organisms (e.g., fish) and semi-aquatic wildlife (e.g., shorebirds).
Terrestrial and semi-aquatic birds (e.g., shorebirds) and terrestrial mammals can be exposed
to chemicals in sediment/soil or surface water from several different behaviors. Animals
can inadvertently or purposefully ingest sediment/soil while grooming, burrowing, or
consuming contaminated prey species. Surface water can be ingested as a drinking water
source or during bathing or grooming activities. Dermal contact with sediment/soil or
surface water is considered a secondary route of exposure for birds and mammals. Dermal
contact is of concern primarily with organic chemicals that are lipophilic (i.e., have an
affinity for fats) and can cross the epidermis of the exposed organism. Although some of the
COPECs (e.g., DDT ) are highly lipophilic and can bioaccumulate, they are of greater
concern in the food chain pathway as opposed to direct contact.
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SECTION 2:PROBLEM FORMULATION
Fish can be exposed to chemicals in sediment and/or surface water through incidental
ingestion, dermal contact, uptake across the gills, and consumption of contaminated aquatic
plants or invertebrates. However, because no suitable model was available to evaluate
food-chain exposures, food ingestion was not included in the evaluation. Fish also serve as
a major route of food chain transfer because they are prey for other fish and semi-aquatic
wildlife.
Exposure through the food chain is limited to chemicals that bioaccumulate. Chemicals can
be accumulated in plants that are consumed by herbivorous animals, which are then
consumed by omnivorous and insectivorous animals, carnivorous animals, and
decomposers. Pesticides, such as DDT and its metabolites, are of primary concern for
bioaccumulation because these chemicals can also biomagnify up the food chain.
2.6 Biota Sampling in Nearby Areas
Aquatic biota similar to those collected within the Bolsa Chica Lowlands (Sections 2.3.1 and
2.5.1) for the ERA have been sampled in nearby areas through other programs. The Seal
Beach National Wildlife Refuge Study (SWDIV 1995) was conducted to assess the effects of
operations at Naval Weapons Station Seal Beach on the biota of the tidal marsh at Seal Beach
National Wildlife Refuge. The study focused on the potential bioaccumulation of chemicals
in species that are the primary food items of the light-footed clapper rail and California least
terns. Results for invertebrates and fish are summarized in Table 2-24.
Fish also were sampled in Anaheim Bay/Huntington Harbour through the Toxic Substances
Monitoring Program (Rasmussen 1995, 1997). Black perch (Embiotoca jacksoni) and barred
surfperch (Amphistichus argenteus) were sampled in 1992-1993 and yellowfin croaker
(Umbrina roneador) were sampled in 1995. Results for these fish are summarized in
Table 2-25. In 1992, the fish contained elevated levels of total chlordane and total DDT, and
in 1993 they contained elevated levels of chromium and total DDT. In 1995, elevated levels
of total chlordane, total DDT, and total PCB were found in fish.
Transplanted California mussels (Mytilus californianus) were sampled at the Warner Avenue
Bridge on Huntington Harbor in 1994 and 1995 (Rasmussen 1996). (Because no suitable
resident population existed there, mussels from Trinidad Head or Bodega Head were
deployed for 4-6 months prior to sampling). Results are presented in Table 2-26. Mussels
contained elevated levels of cadmium, zinc, chlorpyrifos, total chlordane, total DDT,
dieldrin, and total PCB in both 1994 and 1995. In 1994, concentrations of arsenic, lead,
selenium, and oxadiazon also were elevated, and in 1995, chromium, heptachlor epoxide,
and toxaphene were elevated.
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SECTION 3
Analysis
The Analysis phase links the Problem Formulation to the Risk Characterization and consists
of the technical evaluation of chemical and ecological data to determine potential for
ecological exposure and adverse effects. The assessment endpoints and ecological
conceptual site model defined in the Problem Formulation focus the Analysis, which
consists of two components - the Exposure Characterization and the Ecological Effects
Characterization. These two components are used to evaluate the relationships between
receptors, potential exposures, and potential effects. The results of these evaluations provide
the information necessary to determine or predict the potential risks to ecological receptors
from the identified stressors under defined exposure conditions. The products of the
Analysis consist of exposure profiles (from the Exposure Characterization) and stressorresponse
profiles (from the Ecological Effects Characterization) that summarize the
relationships between stressors and responses.
3.1 Exposure Characterization
The Exposure Characterization includes an overview of the field activities conducted as
part of the ERA Sampling and Analyses (CH2M HILL, 1998a) and Focused Sampling and
Analyses (CH2M HILL, 2000); an evaluation of the chemical data for sediment/soil, surface
water, pore water, and biota collected as part of the sampling and analysis, an evaluation
of onsite background conditions for inorganic chemicals, an exposure analysis for the
representative species, and the exposure profile.
3.1.1 Field Sampling and Analysis
The first phase of sampling and analysis (ERA Sampling and Analyses) was designed
to complete the initial sampling for areas away from known or suspected sources of
contamination, to conduct toxicity and bioaccumulation bioassays (using site-collected
sediment or water from “random” and “focused” sites), and to analyze field-collected biota.
The sampled areas include material within the dredging “footprint” for the Full Tidal habitat,
but only that portion just below the depth of dredging. The bioassays for the ERA were
designed to determine acceptable levels of inorganic and organic chemicals in media to which
ecological receptors may be exposed under current or future conditions. Bioassay media
included sediment, surface water, and pore water from random and focused sampling sites.
The second phase of sampling and analysis (Focused Sampling and Analyses) was designed
to evaluate the nature of contamination, if any, associated with previously identified known
or suspected sources (such as sumps, wells, pipelines, maintenance areas, etc.), and to
conduct follow-up sampling of randomly sampled locations where composited samples
contained elevated levels of chemicals. This focused sampling was conducted after the
Scoping Assessment Report and EEC Report were completed.
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SECTION 3: ANALYSIS
The field sampling program is described briefly in this section, and sample collection
locations are shown in Figures 3-1, 3-2, and 3-3. A detailed description of the field sampling
is included in Appendix A and core logs for each sampled location are presented in
Appendix B.
3.1.1.1 ERA Sampling and Analyses
The information collected in the field from the ERA sampling program, along with results of
toxicity and bioaccumulation tests conducted in the laboratory, were used to complete the
EEC Report (CH2M HILL, 1999). ERA Sampling was conducted in areas away from known
or suspected sources of contamination (described as random sampling) and in selected areas
where previous studies identified elevated levels of chemicals or contamination (described
as focused sampling). In addition, toxicity and bioaccumulation bioassays were conducted
using site-collected sediment and surface water from random and focused sites, and fieldcollected
biota were analyzed.
Random sampling was conducted throughout the Lowlands at a density of one sample
location for each area of approximately 4 acres, with at least one sample point located in
each Cell. Samples from up to six contiguous areas within the same Cell were combined to
form a composite, stratified by depth. The surface sample included 0 to 6 inches bgs; the
subsurface sample included the combined mid-depth (18 to 24 inches bgs) and bottom
depth (42 to 48 inches bgs) of the core. Sediment/soil from the expected dredging depth to
2 feet below that depth was sampled and analyzed to determine whether any chemicals
found there are likely to be toxic or to bioaccumulate in exposed organisms. No significant
deviations from the sampling program occurred during sampling activities. Small
adjustments were made in the field to accommodate sample collection (e.g., moving a
sampling location if it fell on a physical structure such as a pipe or other solid obstruction to
allow for collection of a sample).
Samples were analyzed for a defined “suite” of analytes. These suites of analytes were used
for three basic purposes:
• To analyze the sediment/soil (Suites A, B, and C), water (Suite D), and tissue (Suite E)
matrices for contaminants as required for ERA purposes (see Appendix A, Table A-2)
• To furnish contaminant results at low detection limits (Suite C) to ascertain if unknown
contaminants are present that were not covered by the other suites (Suites A and B)
• To confirm that conditions outside the focused sites are suitable for marine organisms. A
detailed Quality Assurance Project Plan (QAPP) was followed during the course of the
sampling and analysis and is included in Appendix C.
Each surface sediment (0 to 6 inches bgs) composite sample was analyzed for a low
detection limit suite of analytes (Suite C). All subsurface sediment (> 6 inches bgs)
composite samples were analyzed for either Suite A or Suite B analytes. Of the random
sampling sites, 24 were selected for sediment and pore water toxicity bioassays, and 10 of
those sediments were also submitted for laboratory bioaccumulation tests. Surface water
ponded in Cells was collected and submitted for Suite D analyses as well as toxicity
bioassays. The random sampling program included a total of 277 core locations generating
158 samples of sediments for analyses (92 for Suite A, 66 for Suite C). A summary of the
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SECTION 3: ANALYSIS
sampling program is included in Table A-1. Biota (terrestrial plants, terrestrial and aquatic
invertebrates, fish, black-necked stilt eggs, and small mammals) were collected at various
locations within the Lowlands (as shown in Figure 3-1).
Focused sampling was conducted to characterize and determine the extent of contamination
of selected known or suspected sites where previous industrial activity took place and to
measure chemicals present in surface water inflows to the Lowlands. In the ERA Sampling
and Analyses phase of the project, sediment samples were taken within the selected sites to
provide media for bioassays and to determine concentrations of contaminants at various
depths; they were analyzed for Suites A, B, or C. Surface water inflow areas were sampled
for pH, conductivity, metals, organochlorine herbicides, and organophosphorus insecticides
during low-flow and storm events.
Table A-2 in Appendix A summarizes the chemical analyses of surface sediments collected
during the field sampling (Suite C), sediments or water tested for toxicity/bioaccumulation
(Suite C or D), and sediment/soil collected from deeper depths within the same sample
cores (Suites A and B). In addition, plant and animal tissues were analyzed for those
chemicals that were likely to bioaccumulate, including metals, organochlorine insecticides,
polychlorinated biphenyls (PCBs) and polycyclic aromatic hyrocarbons (PAHs) (Suite E).
Bird eggs were analyzed using a modified Suite E, which includes all Suite E compounds
except PAHs. Tissue samples resulting from the laboratory bioaccumulation exposures were
also analyzed for contaminants (Suite E).
3.1.1.2 Focused Sampling and Analyses
The purpose of the focused sampling program was to further characterize known or
potential sources of contamination within the Lowlands. The focused sampling sites include
Random Follow-up sites (composite areas sampled during the Random Sampling where at
least one analyte exceeded benchmarks selected by the Technical Committee), CAR sites,
and Partially Characterized sites (previously sampled by Tetra Tech [1996]). The sampling
strategy is discussed in more detail in Appendix A, and the numbers of samples are listed
by facility/feature and analytical suite in Table A-1:
Random Follow-up
Random Follow-up sites are discrete locations sampled during the Random Sampling
program where the composite sample representing those locations had at least one analyte
that exceeded criteria established by the Technical Committee. Calculated LC20 and LC50
values (from the Bolsa Chica ERA), Effects Range-Low (ER-L) and Effects Range-Median
(ER-M) values published by Long et al. (1995), and calculated background levels were used by
the Technical Committee as guidelines in establishing the selection of Random Follow-up sites.
A total of 190 Random Follow-up sites were sampled and are shown in Table A-1 in
Appendix A. Most of the individual random sampling locations were re-sampled to a depth
of 0.5 feet bgs. Boring depths were advanced to the original project depth of 6 feet bgs when
the bottom composite sample exceeded any of the above stated criteria. Selection of analyses
to be performed on the Random Follow-up sites was based on those constituents that
exceeded screening levels set by the Technical Committee on sediment/soil samples at the
intervals where the exceedances occurred at each location. Appendix A provides a complete
listing of analyses performed on the Random Follow-up samples.
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SECTION 3: ANALYSIS
CAR Sites
A total of 233 locations were sampled in CAR sites as part of the focused sampling. Most of
these CAR sites were “Plate 1 Schaefer-Dixon Anomalies,” those areas within project
boundaries identified from aerial photographs to be areas of disturbed morphology,
possibly from industrial or recreational activity (Schaefer Dixon Associates, 1991).
All CAR site borings were advanced to 6 feet bgs. Samples from each boring were collected
at three intervals; 0 to 6 inches, 30 to 36 inches, and 66 to 72 inches. The middle and bottom
intervals from each boring were combined into a single sample.
For those CAR sites that were less than 1 acre, two borings were collected. However, if the
CAR site was less than 0.1 acre then the two top samples were composited together and the
two middle/bottom samples were composited together.
One boring was collected for every acre or partial acre for those CAR sites that are greater
than 1 acre. No horizontal compositing was conducted. All top samples were analyzed for
the “modified” Suite C list of constituents (Table A-2), and middle/bottom samples were
analyzed for the Suite B list of constituents.
A detailed list of the CAR sites, the number of locations and samples within each site, and
the analyses performed are found in Appendix A.
Partially Characterized Sites
The Partially Characterized sites are the focused facilities or features sampled by Tetra Tech
(1996) for which some existing data were available (Figure 3-3). The sampling plan for the
Partially Characterized sites was developed using all existing Tetra Tech and CH2M HILL
data matched to the list of facilities and features. Sampling rates, analyses performed and
depths below ground surface were used in determining whether any additional
characterization was needed at a particular focused site. Some facilities and features, such as
the oil wells and the roads and berms, were sufficiently characterized and are not scheduled
for additional sampling until the delineation phase, during which the extent of the
contamination will be identified.
A total of 76 Partially Characterized sites were sampled. Below is an explanation of the
sampling and analysis plan for each type of facility or feature. A list of Partially
Characterized sites for each type of facility or feature can be found in Appendix A. Note that
some samples were previously collected during the ERA Sampling program (CH2M HILL,
1998a). Specific locations, numbers of samples, and analyses performed in the modified
sampling plan are detailed in Appendix A.
Sumps
Most of the sumps defined by Tetra Tech were less than 1 acre. There is, however, one site
that is approximately 3 acres and one site, a settling basin, that is about 5 acres. For those
sites that are 1 acre or less, two cores were collected in each. The other two sites were
sampled at a density of 1 core per acre. There were 29 sumps sampled during the second
phase of sampling.
Each core was bored down to 6 feet bgs. Three samples were collected from each boring
(surface, mid, and bottom). The surface interval (0 to 6 inches) from the first core at each
sump was analyzed for the modified Suite C list of constituents. All other surface samples at
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SECTION 3: ANALYSIS
each sump were analyzed for the modified Suite A list of constituents. All middle samples
(32 to 36 inches) were also analyzed for the modified Suite A list of constituents. All bottom
samples (66 to 72 inches) were analyzed for the Suite B list. Table A-2 lists the constituents
tested under each suite.
Wet Gas Pipelines
After reviewing the results of previous sampling along the gas lines, it was decided to
collect an additional 10 surface samples every 2,000 feet along the wet gas lines. Each
sample was analyzed for the Suite B list of constituents (Table A-2) plus organochlorine
pesticides and PCBs.
Existing Dry Gas Line
There are approximately 5,500 feet of dry gas line within the Full Tidal area that would have
to be removed in the short term. Sampling of the dry gas line involved boring a core every
2,000 feet underneath or directly next to the pipeline. A total of six surface samples were
deemed necessary to fully characterize the dry gas line within the Full Tidal area. Since
three surface samples were previously collected by Tetra Tech (1996), three were collected.
These samples were analyzed for the modified Suite A list of constituents (Table A-2) plus
organochlorine pesticides and PCBs.
Abandoned Oil Pipelines
Additional sampling and testing was conducted along the approximately 14,000 feet of
abandoned oil pipeline routes in order to define the extent of both lateral and vertical
contamination. Transects of 3 surface samples were collected every 2,000 feet along the
abandoned oil line routes at a right angle to the routes. A total of 18 samples were collected
and analyzed for the Suite B list of constituents (Table A-2). In addition, every other sample
obtained was analyzed for organochlorine pesticides and PCBs.
Existing Oil Pipelines
Because oil lines outside of the Full Tidal Basin will not be removed in the near future, a
decision was made to sample only those oil lines within the Full Tidal area. One surface
sample was collected every 2,000 feet along the oil lines. A total of 11 samples were collected,
and each one was analyzed for the Suite B list of constituents (Table A-2). In addition, every
other sample obtained was analyzed for organochlorine pesticides and PCBs.
Old KOBE Area
The old KOBE area is a 1-acre facility that was sampled by collecting two cores to a depth of
4 feet bgs. A surface (0 to 6 inches), mid (18 to 24 inches) and bottom (42 to 48 inches) sample
was obtained from each boring. The modified Suite A list of constituents was run on both
surface samples and the Suite B list was run on the middle and bottom samples (Table A-2).
Surface Water Inflows
Four surface water inflows were identified for surface sediment sampling. Three of the four
were sampled during the ERA Sampling program (Springdale Pump Station, Seapoint Golf
Course, and Garden Grove - Wintersburg Channel) by CH2M HILL (1999). Sediment/soil
from the fourth location (Edwards Thumb) was collected and analyzed for the modified Suite C
list of constituents (Table A-2), and surface water was analyzed for Suite D constituents.
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SECTION 3: ANALYSIS
3.1.2 Data Evaluation
The chemical data were evaluated for usability in the ERA (as described in this section) and
evaluated for potential risk to representative receptors based on sample location within
specific evaluation areas. The data for specific Cells were combined into evaluation areas
that either currently have or will have similar habitats after the proposed restoration is
completed. These evaluation areas and the Cells included in each one are as follows:
• Bolsa Bay - Inner Bolsa Bay (Cell IB) and Outer Bolsa Bay (Cell OB)
• Garden Grove - Wintersburg Flood Control Channel - Cell 52
• Full Tidal - Cells 1, 1A, 3 through 8, 15 through 18, 43, 44, 51, 58, 59, 61, and 62
• Future Full Tidal - Cells 14, 19 through 40, and 63
• Muted Tidal plus Rabbit Island - Cells 41, 42, 45 through 50, 53, 55, 60, 66, and 67
• Seasonal Ponds - Cells 2, 9 through 13
• Gas Plant Pond Area - Samples collected downgradient of the former Gas Plant (outside
the numbered Cells, just south of Cells 11 and 12)
• Sitewide (biota only) - terrestrial invertebrates that were composited from throughout
the Lowlands
The analytical data used to characterize exposures consist of the sediment/soil, pore water,
surface water, and biota collected previously by Tetra Tech (1996) and by
CH2M HILL/Kinnetics Laboratories during the ERA Sampling and Analyses and the
Focused Sampling and Analyses. These data were compiled into the ERA chemical database
presented in Appendix D in electronic format (CD).
The electronic data obtained for the Tetra Tech Phase II sampling were checked against the
hardcopy to ensure resolution of the items that had precluded their use in the EEC Report
(CH2M HILL, 1999). These items included missing samples or groups of analytes, lack of
identification for tissue samples, and incompatible structure for inclusion in the electronic
database for the EEC Report. During this review, it was found that all of the items could not
be fully resolved. The electronic database was still deficient in some areas including missing
samples (e.g., diesel and waste oil data were not present for surface water), QA/QC samples
included in the data that were not labeled as such, and lack of locational information (i.e.,
northings and eastings). In addition, the electronic data from Tetra Tech did not include
either a method detection limit or reporting limit for those chemicals that were not detected.
Chemicals that were not detected had either a zero (“0”) or a blank entry for the value. This
results in a slight underestimation of the values calculated in the summary statistics because
one-half the reporting limit was still zero for these chemicals.
The electronic Tetra Tech data were corrected to the extent possible. Data available
electronically from Tetra Tech were incorporated into the ERA chemical database. Tetra
Tech data were also not subjected to any addition data validation processes because this was
reported to have been completed by Tetra Tech when conducting the Phase II
Environmental Assessment (Tetra Tech, 1996).
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SECTION 3: ANALYSIS
The quality of the data obtained during the ERA Sampling and Analyses and the Focused
Sampling and Analyses consisted of a review of 100 percent of the samples (Appendix C).
The results were qualified as appropriate and validation flags were added. The validation
flags used consisted of the following:
• U – Not detected
• J – Estimated value
• UJ – Estimated detection limit
• R – Rejected
The results of data quality evaluation processes indicated that overall, the project data
quality objectives for precision, accuracy, representativeness, completeness, and
comparability were met (Appendix C). Those instances which required qualifying the data
are summarized below:
Matrix effects were evident for some analytes based on the matrix spike, surrogate, and field
duplicate results. Most of these were for sediments and biota tissue, and were expected due
to the complexity of the sample matrices. Most of the matrix recovery failures were
associated with the presence of high concentrations of chlorides in the samples. The matrix
spike, surrogate, and field duplicate deviations resulted in approximately 1.5 percent of the
results being qualified as estimated detects (“J”) and estimated nondetects (“UJ”).
Method blanks were analyzed at the required frequency of at least 1 for every
20 environmental samples or one per analytical batch. Phthalates were routinely detected
in the method blanks, but they are ubiquitous and are considered common laboratory
contaminants. The levels found did not exceed the ecological screening benchmarks and
as such were considered acceptable. Method blanks for method SW8720 (semi-volatiles)
routinely indicated that phthalate contamination may have affected the sensitivity required
to meet the project objectives.
• There were calibration difficulties with some of the analytes resulting in a few results
being rejected and some being qualified as estimated detects and non-detects. The
rejections were due to failure to meet the minimum instrument response, and involved
one analyte (2,4-dinitrophenol) for the Random Sampling. Overall, the qualifications due
to calibration difficulties involved approximately 3 percent of the results for Random
Sampling and 0.7 percent for Focused Sampling.
• Several results (107 from Random Sampling, 236 from Focused Sampling) for
semivolatiles, toxaphene, diesel, or waste oil were qualified as estimated values due
to holding time violations. All other results met the holding time requirements.
• About 1 percent of positive results for pesticides and PCB congeners for Random
Sampling and 0.8 percent for Focused Sampling were qualified as estimated due to
differences between the primary and confirmation results exceeding the acceptance
criterion. The differences were mostly due to interference from coeluting Aroclor peaks
when at least one Aroclor was present.
• In samples that contained Aroclors, some of the Aroclor peaks coeluted within the
retention time windows for some of the pesticides on both the primary and confirmation
columns. This made the identification of some of the pesticides that were reported
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SECTION 3: ANALYSIS
questionable. The use of other confirmation techniques, such as gas
chromatography/mass spectroscopy should be considered in the future.
The validated data from the ERA chemical database (including both Tetra Tech and
CH2M HILL samples) were then evaluated for their use in the risk assessment. Data were
retained or eliminated from the ERA database using the following guidelines:
• Media included in the database consisted of field-collected sediment/soil, surface water,
and biological tissue (terrestrial plants, terrestrial and aquatic invertebrates, fish, stilt eggs,
and small mammals) and polychaete worm tissues from the bioaccumulation studies.
• Focused and random sampling sites were included in the database for purposes of data
summarization and to evaluate exposure point concentrations. Data from the dredge
sampling (both surface and deep samples) were also included for purposes of evaluating
site-specific background concentrations (see Section 3.1.3); however, only those data that
were collected from the 0- to 2-foot depth after habitat restoration were included in the
data used for exposure and effects evaluations.
• Chemical results with final validation qualifiers of any letter except "U" or "UJ" were
considered detected.
• Chemical results with final validation qualifiers of "U" (nondetect level or sample
quantitation limit) or "UJ" (estimated nondetect level) were considered nondetects and
were evaluated at one-half the sample-specific reporting limit to calculate summary
statistics and exposure point concentrations. It should be noted that the Tetra Tech data
did not include sample-specific reporting limits. If a chemical was nondetect, then the
value reported was “0.” This resulted in a slight underestimation of some statistical
parameters (e.g., mean and 95th UCL) as a “0” was evaluated rather than one-half of a
small value. (For example, if the sample-specific reporting limit was 0.6, but a 0 was
reported, then the value used in the summary statistics would have been 0 instead of
0.3 [one-half of 0.6]).
• Chemical results with a laboratory or validation qualifier of "R" were considered rejected
and were removed from the database.
• Chemical data for abiotic media were retained for all sampling locations within a
given evaluation area if the chemical was detected at least once in a specific medium.
Chemicals that were never detected in a specific medium were considered not present
and were removed from the database. For example, if chemical “x” was detected in at
least one sediment/soil sample in the Full Tidal area, then chemical “x” sediment/soil
data from all sampling locations were retained. If chemical “x” was not detected in any
of the surface water sampling locations, then it was assumed that chemical “x” was not
present in surface water and all associated data were removed from the database.
• Chemical data for biological media (i.e. tissue) were retained for all sampling locations
If the chemical was detected once within the entire Lowlands. Data were not removed
based on detection/non-detection within an evaluation area because tissue data were
used to calculate bioaccumulation factors for the entire Lowlands.
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SECTION 3: ANALYSIS
• Sediment results for nonpolar organic chemicals were normalized for total organic
carbon (TOC) for use in some of the evaluations conducted as part of the exposure
characterization. The normalized value was calculated by dividing the chemical
concentration by the fraction TOC (e.g., 2 percent TOC is 0.02 as a fraction) for each
sample. These results are included with the other bioassay data transformations on
the CD for Appendix D.
Chemical data meeting the data evaluation requirements were retained for further evaluation
in the ERA. The chemicals detected in each medium are presented in Table 3-1. The analytical
data for soil and sediment were also combined as a single exposure medium because both
media will become sediment under the post-restoration habitat types for the Lowlands.
Chemicals were also combined into “totals” for specific groupings. The totals were calculated
from the validated data, using detected values only. Non-detect results were not included in
the total. The chemical groupings and chemicals included in each are listed below:
• Low MW PAHs — anthracene, acenaphthylene, acenaphthene, phenanthrene, fluorene,
naphthalene
• High MW PAHs — benzo(a) anthracene, benzo(a) pyrene, benzo(e) pyrene, benzo(b)
fluoranthene, benzo(k) fluoranthene, benzo(g, h, i) perylene, chrysene, dibenz(a, h)
anthracene, fluoranthene, indeno (1,2,3-cd) pyrene, pyrene
• Total PAHs — low MW PAHs and high MW PAHs
• Total DDT — 4,4’-DDD; 4,4’-DDE; 4,4’-DDT
• Total PCBs — Aroclor 1242, Arochlor 1254, Aroclor 1260
• Total phenols — pentachlorophenol
• Total phthalate esters —bis(2-ethyhexyl)pthalate, butyl benzyl phthalate,
diethylphthalate, dimethylphtalate, di-n-butyl phthalate, di-n-octylphthalate
The data were then summarized by area and are presented in Table 3-2 for sediment/soil,
Table 3-3 for surface water, Table 3-4 for terrestrial plant tissue, Table 3-5 for terrestrial
invertebrate tissue, Table 3-6 for stilt eggs, Table 3-7 for small mammals, Table 3-8 for aquatic
invertebrates, and Table 3-9 for fish. The analyses of tissue data were conducted by taxonomic
group and are presented on the accompanying CD. The summary statistics were completed for
tissue groups (e.g. all terrestrial plants) because they would be used as a group in estimating
exposures. The summaries include number of detects; number of samples; minimum and
maximum reported concentrations; mean, median and 95th percent UCL of the mean; and
the 90th percentile. The raw data (including grain size) are presented in Appendix D.
A brief overview of the data is presented below for each area.
Bolsa Bay
Several chemical groups including metals, pesticides, PAHs, and semi-volatiles were
detected at Bolsa Bay. Metals were found with a high frequency of detection in
sediment/soil, and fish tissue. In fish tissue, 7 of 11 chemicals had a detection frequency of
100 percent. Of the 15 detected metals in sediment/soil, 7 had a detect frequency of
100 percent. All detected metals in surface water had a sample size of two.
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SECTION 3: ANALYSIS
Pesticides were found in sediment/soil, small mammal tissue, aquatic invertebrate tissue,
and fish tissue. Pesticides were detected in sediment/soil with low frequency except for
4’4-DDE, which was detected in 36 of 50 samples. Aquatic invertebrate tissue samples had
highest frequencies of detection in the worm and snail samples. 4,4’-DDD and 4,4’-DDE in
fish tissue were detected in all 14 samples, while dieldrin had detects in 10 of 14 samples.
PAHs were detected in sediment/soil in about half of the samples, and in fish tissue
(approximately 25 percent).
Semi-volatiles were detected in sediment/soil, small mammal tissue, and fish tissue.
Semi-volatiles were detected in sediment/soil about one-half the time. While these chemicals
were found in small mammal tissue, the sample size was only one for all semi-volatiles
except naphthalene, which had a sample size of two. Detects in fish tissue were infrequent.
Full Tidal
The Full Tidal area had various chemicals detected including metals, pesticides, PAHs, and
semi-volatiles. Metals were found in sediment/soil, surface water, stilt egg tissue, terrestrial
plant tissue, small mammal tissue, aquatic invertebrate tissue, and fish tissue. Detection
frequency for metals in sediment/soil was very high. Sample sizes ranged up to 382. While
metals were detected in almost all surface water samples, the sample size was two. Sample
sizes for terrestrial plant tissues was only two and metals were detected in both samples.
Metals detected in stilt eggs were numerous and frequent, as were metals in small mammal
tissue. Aquatic invertebrate tissue samples had detects in almost all samples. Fish tissue
samples had 10 detected metals with 6 of those metals being detected in all samples.
Pesticides were detected in sediment/soil but frequency was low. Dieldrin and endrin were
detected in one of two surface water samples. Some pesticides detected in stilt eggs such as
4’4-DDE, 4’4-DDT, BHC-beta, dieldrin, and endosulfan II had frequencies of detection above
80 percent. Pesticides were detected in small mammal tissue, although sample sizes did not
exceed three. Pesticides detected in aquatic invertebrate tissue samples were infrequent.
Fish tissue had infrequent detects of pesticides with the exception of 4’4-DDD, 4’4-DDE, and
dieldrin which were detected in 9 of 10 samples.
PAHs in sediment/soil were detected in less than 10 percent of samples. PAHs were also
detected in small mammal tissue samples although there was only one sample. Detects of
PAHs in fish tissue were also noted, most with a frequency of detection of 30 percent.
Semi-volatiles were detected in sediment/soil and tissue samples but detection was rare.
Future Full Tidal
Metals, pesticides, PAHs, and semivolatiles were all detected in the Future Full Tidal area.
Metals were detected in sediment/soil at a high frequency. In surface water, several metals
were detected; dissolved copper, lead, and zinc were detected in 100 percent of the samples.
Terrestrial plant tissue, aquatic invertebrate, fish tissue, and stilt egg samples also had high
frequency of metal detects.
Pesticides were detected in sediment/soil, surface water, stilt eggs, small mammal tissue,
aquatic invertebrate tissue, and fish tissue. Sediment/soil samples had very few detects and
large sample sizes, with the exception of 4’4-DDD and 4’4-DDE, which were both detected
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SECTION 3: ANALYSIS
in more than one-half the samples. Surface water samples had less than 20 percent detection
frequency for pesticides. Small mammal tissues had various pesticide detects up to
60 percent. Aquatic invertebrate samples had few pesticide detects, with the exception of
4’4-DDD. Fish tissue also had relatively few detects, although 4’4-DDD and 4’4-DDE were
found in all 12 samples.
PAH detects were relatively infrequent and occurred in sediment/soil, small mammal
tissue, worm and fish tissue. Small mammal samples and fish tissue had frequencies of
approximately 50 percent.
Semi-volatiles were occasionally detected in sediment/soil samples although sample sizes
were large and detects were low.
TPH-diesel and waste oil were found in sediment/soil and surface water. Frequency of
detection was greater in surface water.
Garden Grove - Wintersburg Flood Control Channel
Detected chemical groups in the flood-control channel include metals, pesticides, PAHs, and
semi-volatiles. Metals were detected in almost all sediment/soil samples. In surface water,
metals were detected frequently although sample size was small.
Overall, pesticides were detected in less than one-half the sediment/soil samples.
Exceptions include 4’4-DDD and 4’4-DDE, which were detected in 4 of 7 samples.
PAHs, on the other hand, were most often detected in more than one-half of the
sediment/soil samples.
Semi-volatiles were detected often in sediment/soil samples, and most were detected more
than 80 percent of the time.
Gas Plant Pond Area
Detected chemicals include metals, pesticides, PAHs, and semi-volatiles. Several metals
were detected in all sediment/soil samples, while others were detected in only some.
Terrestrial plant, aquatic invertebrate, small mammal, and fish tissue all had small sample
sizes with several metal detects.
Pesticides were detected in sediment/soil, fish, small mammal, and aquatic invertebrate
tissue. All sample types had small sample sizes.
PAHs were detected in sediment/soil samples, but generally occurred in fewer than
10 percent of samples.
Semi-volatiles were rarely detected in sediment/soil samples.
TPH-Diesel and waste oil were the most commonly detected analytes in the Gas Plant Pond
area in sediment/soil and surface water samples.
Muted Tidal Plus Rabbit Island
Samples from the Muted Tidal area were found to contain metals, pesticides, PAHs, and
semi-volatiles. Metals were found in sediment/soil at high frequency. Several metals
occurred in more than 80 percent of samples. Chromium, mercury, selenium, zinc, and
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copper were detected in all five stilt egg samples. Other metals were detected with much
lower frequency. Terrestrial plant tissue also had high metal detect frequencies. Almost all
small mammal tissues had metal detects. Mercury, cobalt, and cadmium were the only
metals not found in every sample. Several metals were detected in aquatic invertebrate
samples, with only a few being detected in less than 50 percent of samples.
Pesticides in sediment/soil were low except for 4’4-DDE and 4’4-DDD. Stilt eggs had a high
number of detects for BHC-beta, dieldrin, 4’4-DDT and 4’4-DDE. Aldrin was also detected
in small mammal tissue in 9 of 12 samples.
PAHs and semi-volatiles were detected in various media, but numbers of detects were low.
Waste oil was found in 54 percent of sediment/soil samples.
Seasonal Ponds
Metals, pesticides, PAHs, and semi-volatiles were all found in the Seasonal Ponds area.
Metals were detected in high numbers in sediment/soil samples. Surface water samples
were found to contain some metals although detection was infrequent in most cases. Copper
and zinc, however, were found in all samples. All metals except nickel were found in all
three stilt egg samples. Terrestrial plant tissue was also found to contain several metals.
While sample size for small mammals is only two, the frequency of detection for metals was
almost always 100 percent.
Pesticide detects were relatively infrequent in the seasonal ponds except for 4’4-DDE in
sediment/soil (25 of 49 samples).
Both PAHs and semi-volatiles were detected, but frequencies were low.
Surface water samples had TPH-diesel and waste oil detects in 100 percent of the samples.
3.1.3 Background Evaluation
An evaluation of inorganic constituents in onsite sediments was conducted for the Bolsa
Chica Lowlands. This evaluation was intended to establish the background (ambient) levels
for metals, as described below. Normally, a background evaluation is conducted by a
statistical comparison of the levels of inorganic constituents from samples collected on site
to a body of data representative of local conditions but which are unaffected by site-related
activities (Cal/EPA, 1997). The background values were used in evaluating potential sources
and spatial distribution of COPECs (Section 3.1.4.1) and for developing site-specific sediment
toxicity values using regression analyses (Section 3.2.1.3). They will also be used in the future
to assist in the development of cleanup goals, which will be part of a separate deliverable.
They were not used to screen out chemicals in the COEC selection process. Specifically, all
detected chemicals were taken through the risk screening process to determine COECs.
Chemicals were not excluded from the risk screening based on comparisons to background.
Given the unique ecological and geologic conditions associated with the Bolsa Chica
Lowlands, the Technical Committee decided that the background evaluation would be
based entirely upon analysis of sediment samples collected onsite. To complete the
background evaluation for the Lowlands, the analytical results from the sediment samples
associated with the ERA Sampling and Analyses (including samples from the proposed
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SECTION 3: ANALYSIS
dredge footprint) were grouped together. (The analytical results from the Focused Sampling
and Analyses and the Tetra Tech Phase II sampling were not included in the development
of the background values). Using samples from potentially contaminated areas (i.e., focused
sites) is reasonable because even if the samples have been contaminated with one or more
metals, they may still have background levels for a number of other metals (Cal/EPA, 1997).
The reported analytical values for all samples that were considered as non-detects (i.e., those
results accompanied by the laboratory flag “U” or "UJ") were evaluated at one-half the
reporting limit. All other laboratory results were left unchanged. This transformed data set
was then plotted in a manner similar to the method for displaying analytical data shown in
the Cal/EPA (1997) guidance for evaluating inorganic constituents. The transformed data
were sorted in order of ascending concentration for each metal and plotted against the
cumulative percent of samples. The cumulative percent plots for selected inorganic
constituents are included in Appendix E. Where available, sediment screening benchmark
values (Low and Median Effect Range [ER-L and ER-M] after Long et al., 1995 and other
sources) are also provided on the cumulative percent plots for comparative purposes.
When inorganics are measured for a relatively large number of background or site soils, the
plotted cumulative percent curves describe a distribution of the sample results. When only
a few data points are available, the distributions of inorganic levels are more difficult to
describe and often only the central tendency may be described with confidence. When
large data sets are available, the extremes of distribution are more easily characterized.
Depending on the size of the background sample data set, an upper percentile (e.g., 95th
or 99th) might be considered an appropriate criterion for the upper range of background
conditions (Cal/EPA, 1997).
To estimate the background levels for selected metals, each of the cumulative percent plots
was examined for certain characteristics as described in Appendix E. For most metals, nondetected
sample data were kept within the data sets although these data were represented
as one-half the reporting limit. There were only five metals for which the nondetects
appeared to significantly affect the cumulative distributions (see text below). The estimated
break point between the background and apparently elevated concentrations for the three
sample groups (all sample, surface, and subsurface) of each element, along with the
percentile values and sample size summary, are presented in Table 3-10. Although the
background evaluation results for all three groups are presented, the estimated background
level for each of the selected inorganics was consistently taken from the all sample group.
The percentile values corresponding to the break point values are reported in Table 3-10 but
the percentile values were not used as a selection criterion for the break point.
In addition to the short descriptions of background levels given below for the selected
inorganics, selected cumulative percent plots are also included to illustrate how the
background levels were determined. Figure 3-4 shows the cumulative percent curve for
copper, with an arrow showing the break point for the distribution of sample concentrations
for this constituent. Break points were chosen in a similar manner for the other selected
inorganic constituents where the cumulative percent distribution shows a distinct point
where a marked slope increase was noted.
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SECTION 3: ANALYSIS
For five of the selected elements (cadmium, mercury, selenium, silver, and thallium), the
data sets contained a relatively large number of samples that were classified as nondetects
(i.e., flagged with “U” in the analytical database). Even though these nondetect reported
values were divided by 2, the reporting limits were elevated enough so that the sample
entries were still observed as elevated concentrations in the cumulative percent plots (for
examples refer to Figure 3-5a and Figure 3-6a).
In these cases, the cumulative percent plots did not clearly show a single break point
between background and elevated concentrations because the plots show two separate
locations where sample concentrations rise steeply. To clarify the break point between
background and elevated levels for these constituents, the cumulative percent plots were
regenerated with the nondetect entries removed from the data sets. Examples of the
regenerated cumulative percent plots are provided in Figure 3-5b for selenium and
Figure 3-6b for silver, which show a single break point once the nondetect entries are
removed.
Arsenic
Background levels of arsenic in the Bolsa Chica Lowland sediments are estimated to be
< 11 mg/Kg dw. This value was relatively consistent among surface, subsurface samples,
and the entire sample group. For surface samples, this background level represents the 88th
percentile (i.e., 12 percent of the samples tested had concentrations above this value). This
concentration represented the 95th and 91st percentile for subsurface samples and all
samples, respectively. All three cumulative percent plots for arsenic (surface, subsurface,
and all sample groups) rise in a smooth line to the break points, where the curves become
less smooth as they rise more sharply (Appendix E, Figures E-1 through E-3).
Barium
Background levels of barium in the Bolsa Chica Lowland sediments are estimated to be
< 110 mg/Kg dw based on the evaluation of the all sample data sets. This value represents
the 89th percentile for the all sample group. When the surface samples were considered
alone, a background level of < 92 mg/Kg dw was estimated (81st percentile level). When
the subsurface samples were considered, a background level of < 75.9 mg/Kg dw was
estimated (86th percentile level). All three cumulative percent plots for barium rise in a
smooth line to the break points, where the curves become less smooth and rise more sharply
(Appendix E, Figures E-4 through E-6).
Beryllium
Background levels of beryllium in the Bolsa Chica Lowland sediments are estimated to be
< 0.94 mg/Kg dw based on the evaluation of the all sample data set. This value represents
the 91st percentile for the all sample groups. When the surface samples were considered
alone, a background level of < 0.88 mg/Kg dw was estimated (83rd percentile level).
When the subsurface samples were considered alone, a background level of < 0.8 mg/Kg dw
was estimated (95th percentile level). The differences among the surface, subsurface, and all
sample values are probably not significant. All three cumulative percent plots for beryllium
rise in a smooth to slightly stepped line to the break points, where the curves rise more
sharply (Appendix E, Figures E-7 through E-9).
ERA REPORT 3-14 SAC/143368(003.DOC)
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SECTION 3: ANALYSIS
Cadmium
Background levels of cadmium in the Bolsa Chica Lowland sediments are estimated to be
< 0.66 mg/Kg dw. This value represents the 91st and 95th percentile levels for the all sample
and surface data sets, respectively. This data set had a large number of nondetect values
(i.e., flagged with “U” in the database) that occur at higher concentrations in the data set.
The resulting cumulative percent plots (Appendix E, Figures E-10a, E-11, and E-12) show
a two-stepped curve. There were 368 samples out of the total 581 samples that were nondetects.
The same value (0.66 mg/Kg) was at the 91st percentile level for the all sample data
set when the nondetect values were removed. The resulting cumulative percent plot
(Appendix E, Figure E-10b) shows a smooth curve rising to the break point, where the curve
becomes discontinuous and starts to rise more steeply. A similar value of < 0.65 mg/Kg dw
was estimated from the subsurface sample data set (86th percentile).
Chromium
Background levels of chromium in the Bolsa Chica Lowlands are estimated to be
< 43 mg/Kg dw. This value represents the 94th and 90th percentile value for the all sample
and surface data sets, respectively. A lower value (< 32 mg/Kg dw) was estimated from the
subsurface sediment samples that represents the 96th percentile value for that data set. All
three cumulative percent plots for chromium rise in a relatively smooth line to the break
points, where the curves become less continuous and begin to rise more sharply
(Appendix E, Figures E-13 through E-15).
Cobalt
The background level of cobalt for the Bolsa Chica Lowlands was estimated to be
< 10.1 mg/Kg dw. This value represents the 93rd and 94th percentile value for the all
sample and subsurface groups, respectively. A slightly lower value (< 10 mg/Kg dw) was
estimated from the surface sediment data, representing the 91st percentile level. All three
cumulative percent plots for cobalt rise in a relatively smooth line to the break points,
where the curves become less continuous and begin to rise more sharply (Appendix E,
Figures E-16 through E-18).
Copper
Background levels for copper in the Bolsa Chica Lowland sediments were estimated to be
< 26.1 mg/Kg dw. This value was derived from the all sample data and represented the 91st
percentile level. A slightly higher value was estimated from the surface (< 30 mg/Kg dw)
sediment sample data set (91st percentile). A lower value was estimated from the subsurface
(< 20.6 mg/Kg dw) sediment sample data set (94th percentile). Figure 3-2 shows the
cumulative percent plot for all the copper samples and the break point in the curve where
the upper limit of the background level was estimated. All three cumulative percent plots
for copper rise in a relatively smooth line to the break points, where the curves begin to rise
more sharply (Appendix E, Figures E-19 through E-21).
Lead
Background levels for lead in the Bolsa Chica Lowland sediments were estimated to be
< 48 mg/Kg dw. This value represents the 95th and 92nd percentile levels for the all sample
and surface data sets, respectively. A lower value of < 17.3 mg/Kg dw was estimated from
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SECTION 3: ANALYSIS
the subsurface sediment samples and represents the 97th percentile value. All three
cumulative percent plots for lead rise in a relatively smooth line to the break points, where
the curves become less continuous and begin to rise more sharply (Appendix E, Figures E-22
through E-24).
Mercury
Background levels for mercury in Bolsa Chica sediments were estimated at < 0.28 mg/Kg dw.
This value represents the 98th percentile for the all sample data set. When only detected
values were considered in the all sample data set, the value represents the 93rd percentile. A
value of < 0.23 mg/Kg dw (96th percentile) was estimated from surface sediment data set and
a value of < 0.15 mg/Kg dw (95th percentile) was estimated from the subsurface sediment
data set. This data set also had a large number of nondetect values with 391 samples out of the
total 581 samples that were flagged as nondetects. The resulting cumulative percent plots
(Appendix E, Figures E-25a, E-26, and E-27) show a two-stepped curve. When only the detect
values were considered, the resulting cumulative percent plot shows a smooth curve to the
break point, where the curve starts to rise more steeply (Appendix E, Figure E-25b).
Nickel
Background levels for nickel in the Bolsa Chica Lowland sediments were estimated to be
< 30 mg/Kg dw. This value represents the 95th and 93rd percentile levels for the all sample
and surface data sets, respectively. A lower value of < 19.1 mg/Kg dw was estimated from
the subsurface sediment samples and represents the 95th percentile value. All three
cumulative percent plots for nickel rise in a relatively smooth line to the break points, where
the curves become less continuous and begin to rise more sharply (Appendix E, Figures E-28
through E-30).
Selenium
The background levels for selenium in Bolsa Chica sediments were estimated at
< 0.54 mg/Kg dw. This value represents the 78th and the 96th percentile values for the all
sample and surface data sets, respectively. When the nondetect values are removed, this
value represents the 94th percentile value for the all sample group. The different cumulative
percent plots for the two data sets are presented in Figures 3-5a and 3-5b. The break point
on the cumulative percent plot without nondetects (Figure 3-5b) provides a clearer view of
the change in slope for selenium concentrations. The estimated values for the subsurface
(< 0.49 mg/Kg dw) sediment samples were similar to that estimated from the all sample
and surface sample groups. This data set also had a large number of nondetect values with
368 samples out of the total 580 samples that were flagged as nondetects. The resulting
cumulative percent plots for selenium (Appendix E, Figures E-31a and E-33) show a stepped
curve. The cumulative percent plots for the surface sediments (Figure E-32) and the all
sediment plot with only the detected values (Figure E-31b) show a smooth curve to the
break points, where the curves become discontinuous and rise more steeply.
Silver
The background level for silver in Bolsa Chica sediments is estimated to be < 0.22 mg/Kg dw.
This value represents the 80th percentile value for the all sample data set. As was done for
selenium, the all sample data set was also plotted without nondetect values in order to more
ERA REPORT 3-16 SAC/143368(003.DOC)
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SECTION 3: ANALYSIS
easily identify the curve break point. In the latter case, the < 0.22 mg/Kg dw value represents
the 86th percentile level. Both cumulative percent plots are provided for comparison (see
Figures 3-6a and 3-6b). A slightly lower background level (< 0.19 mg/Kg dw) was estimated
from the surface sediment data set (97th percentile value). Because there were only 2 samples
out of 264 samples that were actually detects in the subsurface sample group, the background
level was not assessed for this limited data set. The all sample data set had a large number of
nondetect values with 539 samples out of the total 581 samples that were flagged as nondetects.
The cumulative percent plot for silver (Appendix E, Figures E-34a) shows a stepped curve. The
cumulative percent plots for the all sediment group with only the detected values (Figure E-34b)
shows a relatively smooth curve to the break point, where the curve becomes discontinuous and
rises more steeply. The break point on the cumulative percent plot for the surface sediments
(Figure E-35) was found to occur at the end of the first continuous string of actual detected
values, where the curve starts to rise more steeply. Due to the large number of nondetect values
in the subsurface sediments, a break point was not assessed (Figure E-36).
Thallium
The background level for thallium in Bolsa Chica sediments is estimated to be
< 0.61 mg/Kg dw. This value represents the 81st percentile value for the all sample group and
the 99th percentile when the nondetect values are removed from the data set. Slightly lower
values were estimated from the surface (< 0.52 mg/Kg dw) and subsurface (< 0.44 mg/Kg dw)
sediment data sets. This data set had an elevated number of nondetect values with 159 samples
out of the total 581 samples that were flagged as nondetects. All three cumulative percent
plots for thallium rise in a relatively smooth line to the break points, where the curves begin
to rise more sharply (Appendix E, Figures E-37 through E-39).
Vanadium
The background levels for vanadium in Bolsa Chica sediments are estimated to be
< 75 mg/Kg dw. This value represents the 91st percentile value for the all sample data set.
A slightly lower value (< 72 mg/Kg dw) was estimated from the surface sediment sample
group that represents the 84th percentile value. A lower level (< 60 mg/Kg dw) was
estimated from the subsurface sample group that represents the 93rd percentile value. All
three cumulative percent plots for vanadium rise in a relatively smooth line to the break
points, where the curves begin to rise more steeply (Appendix E, Figures E-40 through
E-42).
Zinc
The background level for zinc in Bolsa Chica Lowland sediments is estimated to be
< 103 mg/Kg dw. This value represents the 91st percentile value for the all sample data set.
Lower levels were estimated from the surface (< 92 mg/Kg dw) and the subsurface sample
group (< 89.7 mg/Kg dw) that represent the 81st and 97th percentile values, respectively.
All three cumulative percent plots for zinc rise in a relatively smooth line to the break
points, where the curves become less continuous and begin to rise more steeply
(Appendix E, Figures E-43 through E-45).
SAC/143368(003.DOC) 3-17 ERA REPORT
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SECTION 3: ANALYSIS
3.1.4 Exposure Analysis
The exposure analysis establishes a relationship between stressors at the site (e.g.,
concentrations of COPECs) and the potential ecological receptors. Information used to
establish this link includes site information on sources of stressors, and the spatial
distribution of COPECs across the site, estimates of exposure point concentrations, and
calculations of reasonable maximum daily dosages from chemical accumulation in the food
chain for terrestrial and semi-aquatic birds and terrestrial mammals.
3.1.4.1 Potential Sources and Spatial Distribution of Chemical Stressors
The sources of chemical stressors in the Bolsa Chica Lowlands were described in
Section 2.1.3, and Section 2.1.4, and will only be summarized here. The Bolsa Chica
Lowlands consist of approximately 1,211 acres of terrestrial, wetland, and marine/estuarine
habitats. The watersheds that drain into the site are extensive and highly urbanized. Historic
use of the site and surrounding areas has included livestock grazing, crop farming, oil and
gas production, and recreational. The primary use of the site since the 1940s has been for oil
and gas exploration, production, and processing.
Potential sources of COPECs include agricultural activities, hunting using lead shot, oil and
gas production, and nonpoint source pollution. Farming activities and agricultural runoff
could contain metals, fertilizers, and pesticides. Numerous activities associated with oil and
gas production result in releases of metals, PAHs, and PCBs; stormwater/urban drainage
could contain various chemicals, including metals, pesticides, herbicides, and PAHs.
The Bolsa Chica Lowlands have little surface topography other than a network of roads
and levees that divide the site into approximately 60 Cells. Groups of these Cells, based on
habitat and planned restoration, were considered evaluation areas for estimating potential
risks to less mobile ecological receptors during the Risk Characterization.
The GIS database was queried, based on randomly located samples, to determine which
Cells had sample analytical values that exceeded preliminary screening values. These
queries were completed for five different chemical groups including metals, petroleum
hydrocarbons, chlorinated pesticides, PCBs, and phthalates. The preliminary screening level
was based on conservative effect measures including the LC 20 or the ER-L. In addition,
metals were also screened against the estimated background levels. A secondary screening
was also conducted that used a less conservative effect measure (LC 50 or ER-M). The results
of the screening are presented graphically in Figures 3-7 through 3-16.
The GIS database queries showed that random samples from seven Cells did not exceed any
screening level for any analyte. These Cells are the same on each of the Figures 3-7 through
3-16 and include Cell 5, Cell 8, Cell 14, Cell 16, Cell 17, Cell 18, and Cell 59. Random samples
from several of those Cells were taken in the depth interval of 0 to 2 feet below expected
dredge depth. The figures also show that there were no random samples from Cell 23 and
Cell 24 (comprising the location of the former waste handling facility) since this entire area
was considered only for focused sampling.
The results of the preliminary screening generally indicated a large number of Cells where
at least one screening level was exceeded for metals, petroleum hydrocarbons, chlorinated
pesticides, and phthalates. Exceedances of PCBs were far less widespread based on
ERA REPORT 3-18 SAC/143368(003.DOC)
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SECTION 3: ANALYSIS
preliminary screening. As expected, the corresponding number of Cells where the
secondary screening levels (ER-Ms or LC 50 s) were exceeded was much smaller than for the
preliminary screening level. Chemical group-specific discussions are presented below:
Metals
Exceedances of the preliminary screening levels (LC 20 , ER-L, or background levels) were
observed in most Cells within the Bolsa Chica Lowlands. Exceedances of the preliminary
screening levels were not observed in the seven Cells listed above or in Cell 6, Cell 37,
Cell 49, Cell 58, or Cell 60 (Figure 3-7).
One or more exceedances of the ER-M for individual metals were observed in only 4 Cells:
Cell 1A, Cell 3, Cell 34, and Cell 35 (Figure 3-8).
Petroleum Hydrocarbons
Exceedances of the preliminary screening levels (LC 20 or ER-L) were observed in most Cells
within the Bolsa Chica Lowlands. Exceedances of the preliminary screening levels were not
observed in the seven Cells listed above or in Cell 9, Cell 10, Cell 13, Cell 19, Cell 25, Cell 31,
Cells 38 through 45, Cell 50, Cell 51, Cell 61, Cell 62, or Cell 67 (Figure 3-9).
One or more exceedances of the secondary screening levels (LC 50 ) for petroleum
hydrocarbons were observed in only 6 Cells: Cell 1A, Cell 3, Cell 4, Cell 21, Cell 34, and
Cell 36 (Figure 3-10).
Chlorinated Pesticides
Exceedances of the preliminary screening levels (LC 20 or ER-L) were observed in most Cells
within the Bolsa Chica Lowlands. Exceedances of the preliminary screening levels were not
observed in the seven Cells listed above or in Cell 4, Cell 6, Cell 14, Cell 21, Cell 25, Cell 31,
Cell 37, Cell 39, Cell 47, Cell 62, or Cell 67 (Figure 3-11).
One or more exceedances of the secondary screening levels (ER-M) for chlorinated
pesticides were observed in 11 Cells: Cell 1, Cell 15, Cell 26, Cell 30, Cell 32, Cell 35, Cell 42,
Cell 46, Cell 52, Cell 53, and Cell 58 (Figure 3-12).
PCBs
Exceedances of the preliminary screening levels (LC 20 or ER-L) were observed in fewer Cells
within the Bolsa Chica Lowlands than for other chemical groups. Exceedances of the
preliminary screening levels were observed in 6 Cells: Cell 1A, Cell 26, Cell 34, Cell 36, Cell
47, and Cell 52, as well as Inner Bolsa Bay (Figure 3-13).
One or more exceedances of the secondary screening levels (ER-M) for PCBs were observed
in only 2 Cells, Cell 26 and Cell 47 (Figure 3-14).
Phthalates
Exceedances of the preliminary screening levels (LC 20 ) were observed in fewer Cells within
the Bolsa Chica Lowlands than for other chemical groups except PCBs. Exceedances of the
preliminary screening levels were observed in 15 Cells: Cell 1A, Cell 3, Cell 7, Cell 9, Cell 12,
Cell 21, Cell 26, Cell 32, Cell 34, Cell 36, Cell 42, Cell 45, Cell 48, Cell 49, and Cell 63, as well
as Inner and Outer Bolsa Bay (Figure 3-15).
One or more exceedances of the secondary screening levels (LC 50 ) for phthalates were
observed in only 3 Cells: Cell 7, Cell 21 and Cell 36 (Figure 3-16).
SAC/143368(003.DOC) 3-19 ERA REPORT
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SECTION 3: ANALYSIS
3.1.4.2 Exposure Point Concentrations
A conservative approach was used to define the exposure point concentrations for receptors
in the Bolsa Chica Lowlands due to the future uses of the Lowlands as mitigation habitat and
a wildlife refuge. The exposure point concentrations for abiotic media (intake or contact with
sediment/soil, surface water, and pore water) were calculated based on the mobility of the
receptor being evaluated and the availability of data (i.e., were sufficient samples available to
calculate specific statistics?). The exposure point concentrations for biotic exposure media
(i.e., intake of food items) were calculated from data collected over the entire site for each tissue
type. This combination of tissue data was used primarily because the higher trophic level
receptors are not limited to foraging within a single cell and may forage throughout the site.
Abiotic Exposure Media
The exposure point concentrations for abiotic exposure media (sediment/soil and surface
water) that will be used in exposure and risk estimates for terrestrial and aquatic plants and
invertebrates are the maximum detected concentration for each detected chemical in each
evaluation area (e.g., Full-tidal). This value was selected because plants and invertebrates
are either immobile or relatively sedentary receptors, so they do not spatially average their
exposure over the medium in which they reside (Suter et al., 2000).
The exposure point concentrations for fish were selected based on the physical limitations to
their mobility (they are unable to move between cells), and the limited availability of surface
water data. For most analytes and evaluation areas, sample sizes were not greater than
5 samples (Table 3-3) precluding the calculation of a 95-percent UCL. In addition, reference
toxicity values were not available for some chemicals with greater than 5 samples (e.g., TPH
diesel and waste oil). Based on the future uses of the Lowlands, the limited mobility of fish
in the Lowlands, and the availability of surface water data, the observed maximum
concentrations detected in each evaluation area were selected as the exposure point
concentrations for fish.
The exposure point concentrations for birds and mammals are the 95-percent UCLs of the
arithmetic mean where a 95th UCL could be calculated and it was lower than the maximum
reported concentration. If a 95th UCL could not be calculated or it was greater than the
maximum, the maximum detected concentration was used. Duplicate samples were treated
as unique samples and the maximum detected concentration (regardless of whether the
duplicate or the original sample had the higher value) was used. The exposure point
concentrations for abiotic media (i.e. maximum detected values and 95-percent UCLs) were
presented in Table 3-2 (sediment/soil) and Table 3-3 (surface water).
The use of maximum exposure concentrations was carefully considered along with the less
conservative alternative approach of using the mean or the 95-percent UCL of the mean.
The selected approach is consistent with standard practice. Plants and invertebrates are
immobile or relatively sedentary receptors, so it is not reasonable to assume that they
spatially average their exposure over the medium in which they reside (Suter et al., 2000).
To determine which chemicals at the site may require cleanup, the maximum concentration
is the most appropriate exposure measure. Because this site is intended to serve as
mitigation habitat, and because it will become a wildlife refuge once remediation is
complete, this approach is appropriate.
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SECTION 3: ANALYSIS
Biotic Exposure Media
Exposure point concentrations for the biota component of the diets for terrestrial and semiaquatic
birds and terrestrial mammals were calculated based on tissue samples collected
throughout each of the evaluation areas. Tissue concentrations for field-collected terrestrial
plants, terrestrial invertebrates, bird eggs, small mammals, and fish were combined based
on tissue type (e.g., terrestrial plants collected throughout each group of Cells, regardless of
plant species, were grouped together). A 95th percent UCL was then calculated for the
combined tissue group. The tissue concentrations for field-collected aquatic invertebrates
were combined within evaluation area by species. The different species were not combined
because different representative species would not feed on all the aquatic invertebrates
collected. The exposure point concentration for each aquatic invertebrate species was either
the 95 percent UCL or the maximum detected value, following the same rules as were
applied to the other exposure media. The exposure point concentrations were previously
presented in Tables 3-4 through 3-9.
3.1.4.3 Food Chain Uptake Model
Contact with chemical stressors by higher trophic-level receptors (birds and mammals)
must take into account intake of the various dietary items (biota tissue) that may have
accumulated site contaminants, as well as intake of the abiotic media (sediment/soil and
surface water). Food chain exposure estimates were calculated for representative terrestrial
birds, semi-aquatic birds, and terrestrial mammals for the following exposures:
• Belding's savannah sparrow - ingestion of terrestrial plants, terrestrial invertebrates,
sediment/soil, and surface water
• American kestrel - ingestion of terrestrial invertebrates, terrestrial vertebrates (small
mammals and birds), sediment/soil, and surface water
• Black-necked stilt - ingestion of aquatic invertebrates, sediment/soil, and surface water
• Least tern - ingestion of fish, sediment/soil, and surface water
• Black-crowned night-heron - ingestion of aquatic invertebrates, fish, small mammals,
sediment/soil, and surface water
• Western harvest mouse - ingestion of terrestrial plants, terrestrial invertebrates,
invertebrates, sediment/soil, and surface water
• Coyote - ingestion of terrestrial plants, bird eggs, small mammals, sediment/soil, and
surface water
To address this multiple pathway exposure, modeling was required. The necessary input
parameters to the exposure model are outlined below. Exposure estimates for each
representative species were generated based on model assumptions, life history parameters,
and bioaccumulation factors (presented below), and exposure point concentrations
(presented in Section 3.1.4.2).
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SECTION 3: ANALYSIS
Model
The general form of the food chain model used to estimate exposure of birds and mammals
to COPECs in soil-sediment, surface water, and food items is as follows:
Where:
E t = E o + E d + E i
E t = the total chemical exposure experienced by wildlife
E o , E d , and E i =
oral, dermal, and inhalation exposure, respectively
Oral exposure occurs through the consumption of contaminated food, water, or soil-sediment.
Dermal exposure occurs when contaminants are absorbed directly through the skin. Inhalation
exposure occurs when volatile compounds or fine particulates are inhaled into the lungs.
Although methods are available for assessing dermal exposure to humans (U.S. EPA 1992f),
data necessary to estimate dermal exposure are generally not available for wildlife (U.S.
EPA 1993c). Similarly, methods and data necessary to estimate wildlife inhalation exposure
are poorly developed or generally not available (U.S. EPA 1993c). Therefore, for the
purposes of this assessment, both dermal and inhalation exposure were assumed to be
negligible. As a consequence, most exposure must be attributed to the oral exposure
pathway. By replacing E o with a generalized exposure model modified from Suter et al.
(2000), the previous equation was rewritten as follows:
Where:
N
⎡
⎤
[ j s ] ⎢∑
ij i ⎥ + [ j
× ]
Eo
= Soil × P × FIR + B × P × FIR Water WIR
⎣ i=
1
⎦
E o = total oral exposure (mg/Kg/d)
Soil j = concentration of chemical (j) in soil (mg/Kg)
P s = soil ingestion rate as proportion of diet
FIR = species-specific food ingestion rate (kg food/Kg body weight/d)
B ij = concentration of chemical (j) in biota type (i) (mg/Kg)
P i = proportion of biota type (i) in diet
Water j =
concentration of chemical (j) in water (mg/L)
WIR = species-specific water ingestion rate (L/kg body weight/d)
The end product or exposure estimate for external exposures for birds and mammals is a
dosage (amount of chemical per kilogram receptor body weight per day [mg/Kg bw/d])
rather than a media concentration as is the case for the other receptor groups (fish and other
aquatic organisms, terrestrial plants, and terrestrial invertebrates. This is a function of both
the multiple pathway approach as well as the typical methods used in toxicity testing for
birds and mammals. Sample calculations for exposure via food-chain uptake are presented
in Appendix I, along with examples of risk estimation calculations.
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SECTION 3: ANALYSIS
Summaries of total (i.e., sum over all pathways) and partial (pathway-specific) exposure
estimates are presented and compared to toxicity values in Section 4.1.
Life History Parameters
The specific life history parameters required to estimate exposure of each receptor to
COPECs include body weight, ingestion rates of food and water, dietary components and
percentage of the overall diet represented by each major food type, and approximate amount
of soil and/or sediment that may be incidentally ingested based on feeding habits. These
parameters were obtained primarily from the literature and are presented in Table 3-11.
Bioaccumulation Factors
A critical component for the estimation of external exposure of birds and mammals is
measurements of concentrations of COPECs in wildlife foods. The most preferred data are
direct measurements of concentrations in samples collected from the field. Available data for
concentrations of COPECs in wildlife foods collected from the Lowlands were summarized
in Tables 3-4 through 3-9. Not all food types consumed by the selected avian and mammalian
receptors, nor are all areas within the Lowlands represented. To allow estimation of exposure
to COPECs for all receptors and locations within Bolsa Chica, estimation of concentrations of
COPECs in wildlife foods was necessary. Bioaccumulation factors for each wildlife food type
were developed based on site-specific data. Bioaccumulation factors were calculated where
both abiotic (sediment/soil or water) and biotic (tissue concentrations) were available for
each Cell. The median concentrations of each abiotic and biotic medium (presented in Tables
3-2 through 3-9) were combined within a given Cell and a Cell-specific bioaccumulation
factor (BAF) was calculated using the following equation:
BAF
=
tissue concentration
abiotic medium concentration
( mg / kg)
( mg / kg)
Where:
BAF = chemical-specific bioaccumulation factor for a given receptor group
Tissue concentration = chemical concentrations (mg/Kg) measured in
terrestrial plants, terrestrial invertebrates, aquatic invertebrates, bird eggs, or
small mammals collected from the Bolsa Chica Lowlands
Abiotic medium concentration = chemical concentrations (mg/Kg) measured
in sediment/soil or surface water collected from the Bolsa Chica Lowlands
The BAFs for each receptor and chemical were then combined across all Cells and
summarized as shown in Table 3-12 for sediment/soil and in Table 3-13 for surface water.
The 90th percentile BAF for each chemical was then used in the food chain uptake model
when direct measured tissue concentrations were not available for a given food item within
a given evaluation area.
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SECTION 3: ANALYSIS
3.1.5 Exposure Profile
The exposure profile establishes the linkage between stressors and receptors based on
potential exposure under current and future conditions at the site. This linkage was
established through identification of ecological receptors, identification of potential sources
and spatial distribution of COPECs, calculation of exposure point concentrations for various
exposure media and receptors based on the most likely exposure scenario for each species,
and calculation of reasonable maximum daily dosages for chemical intake from abiotic and
biotic sources by terrestrial and semi-aquatic birds and terrestrial mammals.
For the Bolsa Chica Lowlands, the potential future exposure conditions may be more
important than the current exposure conditions because the site will be restored to various
upland, wetland, and estuarine/marine habitats that will attract a wide variety of wildlife.
As such, the representative species selected for evaluation were those that currently use the
site and are expected to occur there in the future. These species are summarized below:
• Aquatic and semi-aquatic representative species
− Plants — aquatic grasses and forbs
− Invertebrates — benthic macroinvertebrates
− Fish — mosquitofish, topsmelt, killifish, tilapia
− Birds (semi-aquatic) — black-crowned night-heron, black-necked stilt, and least tern
• Terrestrial/upland representative species
− Plants — terrestrial grasses and forbs
− Invertebrates (terrestrial) — insects and spiders
− Birds (upland) — American kestrel and Belding’s savannah sparrow
− Mammals — western harvest mouse and coyote
The potential exposure pathways for current and future receptors were evaluated as part of
the ecological conceptual site model (see Section 2.5). The representative species and
exposure pathways evaluated in the ERA are based on the use of site-specific (fieldcollected)
abiotic and biotic exposure media. These pathways are listed below:
• Terrestrial plants – direct contact via root uptake from sediment/soil
• Terrestrial invertebrates – direct contact and ingestion of sediment/soil
• Terrestrial and semi-aquatic birds – ingestion of biota, sediment/soil, and surface water
• Terrestrial mammals – ingestion of biota, sediment/soil, and surface water
• Aquatic plants – direct contact and root uptake from sediment/soil and surface water
• Aquatic macroinvertebrates – direct contact and ingestion of sediment/soil
• Fish – direct contact and ingestion of surface water
The primary sources of COPECs include oil and gas production, nonpoint source pollution,
and historic farming and hunting activities on or near the site. Exposure point concentrations
for abiotic (sediment/soil and surface water) and biotic (field-collected plants, invertebrates,
bird eggs, small mammals, and fish) exposure media were calculated based on the most
likely exposure area and pathways for selected representative species. Reasonable maximum
daily dosages (presented in Section 4.1) were calculated for intake of the exposure media
mentioned above by terrestrial and semi-aquatic birds and terrestrial mammals.
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SECTION 3: ANALYSIS
This exposure information will be linked to the ecological effects information described in
the next section to estimate potential risks to terrestrial and aquatic receptors in the Risk
Characterization.
3.2 Ecological Effects Characterization
The Ecological Effects Characterization is used to evaluate adverse effects that may result
from varying concentrations of stressors and to link these effects to the assessment
endpoints and ecological conceptual site model.
Effects data that were reviewed and evaluated consisted primarily of site-specific toxicity
and bioaccumulation bioassays for aquatic receptors. In addition, literature and toxicological
reviews were used to supplement the effects data for terrestrial receptors. These effects are
described in the following section and are used to compile a stressor-response profile that is
linked to the exposure profile developed in the previous section to estimate potential risks in
the Risk Characterization (Section 4).
3.2.1 Ecological Response Analysis
To assess the effect of site contaminants on ecological receptors, several toxicity bioassays
and bioaccumulation tests were conducted using environmental media (sediments, pore
water, and surface water) collected from various focused and random sample sites. Bioassay
results were used to calculate no observed effect concentrations (NOEC), lowest observed
effect concentrations (LOEC), effect concentrations for 50 percent of test organisms (EC 50 ),
and lethal concentrations for 50 percent of test organisms (LC 50 ) for chemicals detected in
sediments, pore water, and surface water. These results were further refined by conducting
statistical regression analyses on the sediment and pore water results. Information gathered
on effect levels was compiled into the stressor-response profile description (Section 3.2.2).
3.2.1.1 Toxicity Bioassays
Toxicity bioassays were conducted to establish site-specific effect levels for sediment, pore
water, and surface water. The intent of the bioassays was to simulate future post-restoration
conditions (e.g., flooding). Some of the tested sediment samples required hydration or
salinity adjustment before bioassays could be conducted. The possibility that hydration or
salinity adjustment of those samples might not accurately reflect the eventual sediment
chemistry or bioavailability was considered. It was estimated that a preliminary test to
experimentally determine the necessary incubation time would require several months,
which were not available because of the time constraints of the project. The approach used
represented the best available option and is presented in Appendix F. In addition,
uncertainties related to the bioassay methodologies are presented in Section 4.2.
Quality control evaluations included mortality in controls, responses of test organisms to
reference toxicants, water quality measurements, and specific issues related to
sample-specific manipulation required for toxicity testing including sample hydration and
salinity adjustment for the bioassays, which are discussed as part of the complete bioassay
report (see Appendix F).
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SECTION 3: ANALYSIS
The toxicity bioassays included the following laboratory tests:
• Sediment – Amphipod (percent survival and reburial), polychaete worm (Nereis viriens)
(survival and bioaccumulation)
• Pore Water – Bivalves (larval development and survival)
• Surface water – Topsmelt (survival and growth), Ceriodaphnia (survival and
reproduction), and Mysidopsis (survival, growth, and fecundity)
Several of the sediment samples arrived at the laboratory in a “dry” state (i.e., there was not
sufficient moisture to conduct the amphipod and polychaete worm toxicity tests or extract
pore waters for the bivalve toxicity tests). In addition, the salinity in approximately half of
the sediment samples was outside the tolerance range of the test organisms. The dry
samples were hydrated and the salinity in either wet or dry samples that was out of range
was adjusted to a range of 26 to 35 parts per thousand (ppt) using the following protocol:
1. Wet Samples
• For Sediment Bioassays
−
Amphipod Toxicity Tests
If salinity was within test range, the sediment was overlain with water of
similar (within 5 ppt) salinity and the test was initiated.
If salinity was out of range, it was adjusted by overlying the sediment with
water of appropriate salinity, and gentle aeration was provided to facilitate
water exchange between the overlying and interstitial environments. If
salinity was very high, initial overlying water was deionized water;
subsequent overlying renewals utilized water of salinity approaching the test
salinity objective (25 ppt). Because of the broad tolerance of the test amphipod
(Eohaustorius estuarius), to low salinity, no test sediment required upward
salinity adjustment.
−
Polychaete Bioaccumulation Exposures
Test sediments were added to the exposure tanks and the flow-through
seawater system was activated. Interstitial water was sampled daily after flow
initiation, and worms were added to the tanks when acceptable salinity was
achieved.
• For Pore Water Bioassays
−
−
If salinity was within test range, the pore water was used as the test media.
If salinity was too high, the pore water was diluted to test range with deionized
water.
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SECTION 3: ANALYSIS
2. For Dry Samples
• Seawater was used to hydrate the sediments during the sediment compositing
process. After an equilibration period of at least ten days, pore water was extracted
and its salinity measured.
−
−
If pore water salinity was within range, sediments and pore waters were used as
test media with no adjustment.
If pore water salinity was out of range, sediments and pore waters were adjusted
as described for wet samples.
Sediments
Bolsa Chica sediment samples were evaluated for acute toxicity to the marine amphipod,
E. estuarius, using the procedures outlined in ASTM (1990) guidelines. The tests were
conducted by ToxScan, Inc., of Watsonville, California. Test and control sediments were
sieved, and the salinity, pH, dissolved sulfide, and total ammonia were measured on the
sediment sample pore water to ensure that ammonia and sulfide concentrations were below
threshold limits for E. estuarius. This species was chosen as the test organism for this bioassay
because of its euryhaline characteristics, its relative insensitivity to grain size, and its ability
to perform well in a full range of salinities (2 to 34 ppt). It was anticipated that many
sediments tested would be best served if salinity adjustments could be avoided. It should be
noted that several sediments either required hydration (by addition of seawater) or showed
porewater salinities outside the tolerance limits of Eohaustorius. In such cases, salinity
adjustments were performed prior to testing, using ASTM recommendations for guidance.
Five replicates were randomly assigned to 1-liter glass test jars with enough sediment to
form a 2- to 3-centimeter layer on the bottom of each jar. The sediments were aerated using
a pasteur pipet after settling and then covered with water of appropriate salinity. The test
was started by randomly assigning 20 amphipods to each jar.
The test was conducted for 10 days under static conditions with constant illumination and
aeration in a chamber with a static 15° C ambient temperature. Daily measurements of
temperature, pH, and dissolved oxygen were made in each test jar. At the end of the 10-day
exposure period, the contents of each jar were poured through a sieve, and the surviving
amphipods were counted. Survivors were then placed on a clean (home) sediment overlain
by seawater at 15° C, and the number of amphipods that buried themselves within a 2-hour
period was recorded. Pore water ammonia and dissolved sulfide concentrations were
measured in one replicate of each test sediment at test initiation and at test termination.
Reference toxicant bioassays were performed using cadmium chloride with each batch of
test animals to verify the health and relative sensitivity of that test organism population.
The results of the amphipod bioassay testing, summarized in Table 3-14, show that survival
of the E. estuarius test organisms ranged from 0 percent to 98 percent. Among the test
exposures with surviving organisms, the percent reburial ranged from 22 percent to
100 percent. Survival rates were significantly different from controls in 30 out of 51 samples,
whereas the reburial rates differed significantly in only 3 out of 51 tests. However, 5 tests
had no survivors and thus no test organisms to rebury. Further analysis of these bioassay
data is provided in Section 3.2.1.3.
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SECTION 3: ANALYSIS
The chronic toxicity of contaminants from Bolsa Chica sediments was also evaluated by
ToxScan, Inc., using clam worms, Nereis viriens. Five replicates of each test and control
sediments were randomly assigned to an array of 31-liter, flow-through glass aquaria. After
settling of the sediments, the tanks were attached to the flow-through aerated laboratory
seawater system. The flow was maintained at a rate to allow a 90 percent tank-volume
change every 4 hours, and the interstitial pore water salinity was monitored until it was
compatible with the test organism tolerance.
The test was initiated when 15 worms were added to each test aquarium. Test exposures
were carried out over a 28-day period. Each tank was monitored daily for temperature,
dissolved oxygen, salinity, pH, and any unusual behavior among the test organisms. After
exposure, the contents of each tank were gently rinsed through a screen and the surviving
worms were retrieved and counted.
The results of the sediment toxicity tests using N. viriens did not show any significant
differences in survival from the control sediments (Table 3-14). Chemical concentrations
associated with the NOECs are presented in Appendix G. Further analyses of these bioassay
data are provided in Section 3.2.1.2.
Pore Water
Pore water was extracted from composited sediment samples by centrifugation at 4° C for
30 minutes to generate 4.2 liters of sample. This amount was required to conduct the proposed
chemical and biological analyses. The 4.2-liter amount was attained for all but two samples for
which pore water bioassays were not conducted. Definitive toxicity tests were conducted on
the pore water samples with the bivalve mussel (Mytilus edulis). Mussels were induced to
spawn by thermal stimulation, and the eggs and sperm were collected in separate beakers of
filtered seawater. Fertilization was accomplished by the addition of an appropriate amount
of sperm suspension. After confirming a minimum of 90 percent fertilization, the tests were
initiated when an aliquot of fertilized eggs was pipetted into each test tube that comprised the
four replicates for each sample exposure. Temperature, dissolved oxygen, pH, and salinity
were monitored in “surrogate” containers for each test (concentrations and controls) at the
beginning and end of the test and daily during the 48-hour test exposure period. The mean
number of embryos added to each container was evaluated by counting embryos immediately
after inoculation in separate “surrogate” test tubes.
At the end of the 48-hour exposure period, the contents of each test tube were preserved with
formalin in preparation for microscopic evaluation. After gently mixing the test tube contents,
a 1-mL sample was collected using a pipette and the sample was placed onto a counting slide.
The total number of normal and abnormal larvae was determined based on the presence or
absence of internal tissue inside a complete larval shell. Assuming that abnormal larvae
would not survive, those individuals were counted as mortalities. Percentage survival and
normal development were calculated. Both of these values were corrected for mortality and
normal development associated with the control exposures. Percentage sample associated
with development and survival NOEC, LOEC, EC 50 , and LC 50 were also calculated.
The results of the 45 pore water toxicity tests are summarized in Table 3-14. The maximum
test concentration of these samples ranged from 0.78 percent of sample to 100 percent. NOECs
for larval development and survival ranged from 0.098 percent of sample to 100 percent of
sample. LOECs for larval development and survival ranged from 0.2 percent of sample to
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SECTION 3: ANALYSIS
100 percent of sample. EC 50 s for larval development ranged from 0.2 percent of sample to
100 percent of sample. LC 50 s for survival ranged from 0.17 to 100 percent of sample. However,
many of these were also the maximum sample concentrations tested because of salinity
adjustments to bring the samples into the tolerance range of the test organism. Chemical
concentrations associated with the NOECs, LOECs, EC 50 , LD 50 are presented in Appendix G.
Further analyses of these bioassay data are provided in Section 3.2.2.
Surface Water
Bolsa Chica surface water samples were evaluated for toxicity to topsmelt, Atherinops affinis,
Ceriodaphnia dubia, and Mysidopsis bahia. The toxicity tests for each species are described
below.
Topsmelt
Toxicity tests with topsmelt followed the procedures outlined in U.S. EPA (1995a)
guidelines. The tests were conducted by CH2M HILL at its Corvallis, Oregon, laboratory.
Chronic toxicity of surface waters was tested by using five or six concentrations ranging
from 1 to 100 percent sample. The tests were started by adding five fish per chamber into
five replicate chambers per concentration used.
Upon arrival at the laboratory, salinity of surface water samples ranged from 23 to 99 ppt.
All samples were adjusted to 30 ppt by the addition of either Tropic Marin® sea salts (to
raise salinity) or distilled water (to lower salinity). The test was conducted for 7 days with
daily renewal of the test solutions. Prior to each solution renewal, pH, dissolved oxygen,
and salinity were measured in each test chamber, and any dead fish were recorded and
removed. In addition to the periodic measurements, temperature was monitored on a
constant basis throughout the 7-day test period. Growth was measured by determining the
dry weight of topsmelt at the conclusion of the chronic definitive tests.
Statistical analyses were used to compare the growth and survival data among each test
concentration and the control solutions. IC 25 values (the percent of sample causing a
25 percent reduction in biological measurement, e.g., growth) were calculated for growth
effects in the chronic tests. The NOEC and the LOEC for survival and growth were also
calculated.
The results of the surface water toxicity tests are summarized in Table 3-14. They show that
the percentage of sample resulting in NOECs for development and survival among the test
samples ranged from 30.3 percent of sample to 100 percent of sample. These were also the
highest concentration of each sample that was tested because of the dilution to adjust
salinity within the tolerance range for the test organism. Because there was no effect in any
of the samples, the LOEC, EC 50 , and LC 50 were greater than the tested concentrations.
Further analyses of these bioassay data are provided in Section 3.2.2. Chemical
concentrations associated with the NOECs, LOECs, EC 50 , and LC 50 are presented in
Appendix G.
Ceriodaphnia dubia
Toxicity tests with Ceriodaphnia were conducted following U.S. EPA (1994e) guidelines for
short-term toxicity tests for freshwater organisms. The tests were conducted by ToxScan,
Inc. in Watsonville, California. Upon receipt at the lab, the stormwater monitoring samples
were tested for electrical conductivity. Of the five surface water samples, two had specific
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SECTION 3: ANALYSIS
conductivity within normal range for Ceriodaphnia. The remaining three had conductivity
readings that indicated total dissolved solids would be out of the acceptable range for the
Ceriodaphnia and so these samples were tested using the marine mysid (Mysidopsis bahia) as
described in the next subsection.
The chronic toxicity of the waters was tested using a series of five dilutions ranging from
6.25 to 100 percent site sample. The tests were conducted using 10 test organisms per test
concentration, with only one test organism in each of 10 polystyrene cups for a given test
concentration. The animals were monitored daily for 6 days for survival and reproductive
success. The results of the toxicity tests (Table 3-14) were statistically evaluated against the
control samples. The NOEC for survival and reproduction was 50 percent for both samples,
and the LOEC for survival and reproduction was 100 percent for both samples. The full
bioassay report is presented in Appendix F and chemical concentrations associated with the
NOEC and LOEC values are presented in Appendix G.
Mysidopsis bahia
Toxicity tests with Mysidopsis were conducted following U.S. EPA (1994f) guidelines for
short-term toxicity tests for marine organisms. The tests were conducted by ToxScan, Inc., in
Watsonville, California. As noted above, three of the stormwater monitoring samples had
conductivity readings that indicated that total dissolved solids would be out of the
acceptable range for the Ceriodaphnia, so these samples were tested using the marine mysid
(Mysidopsis bahia).
The sample salinity was adjusted to 25 ppt using Forty Fathoms® Brand Bioassay Grade sea
salt and E-Pure water. The chronic toxicity of the waters was then tested using a series of
5 dilutions ranging from 6.25 to 100 percent site sample. The tests were conducted using
8 replicates for each test concentration with 5 test organisms per replicate. The animals were
monitored daily for 7 days for survival. At the conclusion of the test, each surviving mysid
was microscopically examined to determine its gender, each female was scored for presence
of eggs in the oviduct or brood pouch, and, finally, the dry weight of the surviving mysids in
each replicate was determined. The results of the toxicity tests (Table 3-14) were statistically
evaluated against the control samples. The NOEC for survival, weight, and fecundity was
100 percent in all samples. The LOEC for survival, weight, and fecundity was >100 percent in
all samples. The full bioassay report is presented in Appendix F, and chemical concentrations
associated with the NOEC and LOEC values are presented in Appendix G.
3.2.1.2 Bioaccumulation Tests
The potential for bioaccumulation of contaminants from Bolsa Chica sediments was
evaluated by ToxScan, Inc., using the clam worm, Nereis viriens; these worms were also
monitored to evaluate survival, as described above. The bioaccumulation tests were
conducted using sediment samples collected from a subset of the sample locations; the tests
evaluated the uptake of contaminants by the worms. The complete report for the
bioaccumulation tests is included in Appendix F.
Although most of the test containers received 15 worms in each test aquarium, 5 percent of
the test containers received 25 worms to provide sufficient tissue for quality assurance
(matrix spike/matrix spike duplicate) during tissue chemical analysis. After the 28-day
exposure period, the contents of each tank were gently rinsed through a screen, and the
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SECTION 3: ANALYSIS
surviving worms were retrieved. These worms were placed in filtered, flowing seawater for
24 hours to evacuate their digestive tract. Immediately after this process, the soft tissues were
frozen and stored at –20°C (+5°C) pending chemical analysis to estimate bioaccumulation.
The results of this testing showed that there was significant (p < 0.05) bioaccumulation for
several inorganic and organic analytes, as follows:
• Of 15 inorganic analytes, 3 metals (beryllium, silver, and thallium) were not detected in
any of the test animal tissues. Significant bioaccumulation was noted for barium, cobalt,
copper, lead, mercury, nickel, selenium, vanadium, and zinc. Although detected in test
organisms, there was no significant bioaccumulation noted for arsenic, cadmium, or
chromium.
• Of 22 pesticides and PCBs, only 5 compounds (endosulfan sulfate, endrin ketone,
toxaphene, Aroclor 1424, and Aroclor 1260) were not detected in any test animal tissues.
Significant bioaccumulation was noted for BHC (beta and gamma), chlordane (alpha,
gamma, and technical), 4,4’-DDD, 4,4’-DDE, dieldrin, and Aroclor 1254. Although
detected in test organisms, there was no significant bioaccumulation noted for aldrin,
BHC (alpha and delta), 4,4’-DDT, endosulfan (I and II), endrin, and endrin aldehyde.
• Of 17 PAHs, only 5 compounds were detected in animal tissues, and all showed
significant bioaccumulation. These were acenapthene, anthracene, chrysene, pyrene, and
fluorene.
3.2.1.3 Dose-Response Evaluation
Simple linear regression analyses were performed to determine which contaminants in
sediment and pore water best explained amphipod and Mytilus toxicity bioassay results.
Contaminant concentration data were matched by sample locations with toxicity bioassay
results for each bioassay replicate (i.e., chemical data from a given sample location were
repeated for each bioassay replicate from that location). Because the Mytilus bioassay was
performed using replicates within a series of pore water dilutions at each sample location,
chemical data were also repeated for each dilution. Concentrations within each dilution
were estimated by multiplying the concentration in undiluted pore water from each location
by the reported dilution rate. All nondetects were excluded from the analyses.
As described above and in Appendix F, it was necessary to adjust sediment and pore water
to facilitate performing bioassays. As a consequence, samples on which bioassays were
performed were catagorized into four groups:
• wet, salinity not adjusted
• wet, salinity adjusted
• dry, salinity not adjusted
• dry, salinity adjusted
Regression analyses were performed on all groups pooled and by individual groups, to
determine if modification of the test media influenced toxicity.
Prior to analyses, sediment and pore water data were screened to remove observations that
could potentially confound the analyses (see Appendix F tables F-1 through F-4). All data
from samples in which survival did not differ significantly from controls were included in
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SECTION 3: ANALYSIS
the regression analyses to show the low end of the dose-response curve (e.g., low
concentration/low response). Sediment data that were from samples in which survivorship
differed significantly from the controls were retained for further screening as follows (note:
all screening values, including those derived from the regression analyses are presented as
part of the effects profile at the end of this section):
1. Chemical concentrations were screened against available ER-Ls. Data below ER-Ls were
excluded from the regression analysis for that chemical because it was considered
unlikely that concentrations lower than the ER-L would cause significant mortality.
Instead, the observed mortality was considered more likely to have been caused by
another chemical present in that sample.
2. If the chemical was an inorganic and ER-Ls were unavailable, then concentrations were
screened against the Bolsa Chica background values. Data below the upper limit of
background were excluded from the regression analysis because it was considered
unlikely that chemicals at background levels would cause significant mortality. It was
considered more likely that other chemicals in that sample caused the observed
mortality.
3. If a data point was greater than the ER-L, but lower than background, it was excluded
from the regression analysis if mortality in the bioassay was greater than 50 percent.
Although some toxicity could be expected to occur if chemical concentrations exceeded
the ER-L, it was not likely that mortality would exceed 50 percent even if the
background level for that inorganic chemical was elevated within the Bolsa Chica
Lowlands.
Pore water data were screened as follows:
1. Chemical concentrations were screened against the California Water Quality Standards
for chronic exposure. Concentrations that were below the chronic CTR were excluded
from the regression analyses because concentrations lower than the chronic standard
should not cause significant toxicity. Instead, it was considered more likely that another
chemical in the water sample caused the observed effects.
2. Chemical concentrations exceeding California Water Quality Standards chronic values
were retained for the regression analyses.
3. If a California Water Quality Standard value was not available for a given chemical, it
was retained for regression analyses.
Five out of the 45 total pore water samples contained ammonia. Of these, three samples
(R11C2-1, R32C2-1, and R38C1-1) were considered to have ammonia concentrations that
would be toxic to test organisms, and two (R3C1-1 and FOSN01-1) were considered to have
ammonia concentrations that would potentially be toxic to test organisms. The presence of
ammonia was not clearly tied to significance vs. controls, so the samples were not removed
from the database. Rather, they were screened on a chemical-specific basis for data
reduction for the regression analysis.
The results of this screening process are presented in Appendix F, Table F-1 for sediment
and Table F-2 for pore water. The regression analyses were then performed on data retained
after the screening process had been completed.
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SECTION 3: ANALYSIS
Amphipod (Eohaustorius estuarius) Regression Analysis
Results of the amphipod toxicity bioassay consisted of counts of individuals surviving and
counts of individuals exhibiting reburial behavior. Regression analyses were not performed
for reburial behavior because few significant effects were observed; in more than 50 samples
for which bioassays were performed, significantly decreased reburial was observed in only
3 (see Appendix F).
Sample sizes within each replicate were constant among replicates (i.e., N=20). Therefore,
regression analyses were performed with the count data as the dependent variable. The
independent variables consisted of concentrations of chemicals in sediment (as mg/Kg or
µg/Kg). (Note: TOC-normalized concentrations of organics were evaluated in initial data
screens. As these data did not improve the predictive quality of the regression analyses,
they were not considered further). Because environmental chemistry data are frequently
log-normally distributed (Burmaster and Hull, 1997), analyses were also performed with
natural-log-transformed concentration data as the independent variable. Simple linear
regression analyses were performed using SAS (1994) PROC REG. All models were
considered significant if p#0.05.
Of 75 compounds detected in sediment samples used for amphipod toxicity bioassays based
on all test media adjustment groups combined, significant linear relationships between
untransformed concentrations and survival were observed for 39 (Table 3-15). This
relationship (e.g., slope) was negative for 38 of the 39 compounds. The amount of variation
(r 2 ) explained by these models ranged from 3.7 percent (e.g., r 2 =0.037; lead) to 99 percent
(e.g., r 2 =0.99; total phenol and PCB-028). Natural-log-transformation of the concentrations
resulted in significant fits for 43 of 75 compounds; 39 of them were negative (Table 3-15).
Among these models, r 2 also ranged from 0.033 (e.g., 4,4’-DDD) to 0.99 (e.g., total phenol
and PCB-028). Comparison of the results obtained based on transformed and untransformed
data indicates that, in general, better model fits (e.g., higher r 2 values) were obtained from
the transformed concentration data; untransformed data produced the best fit for
18 analytes whereas 24 analytes were fit best by transformed data (Table 3-15). If total
sample size among all four test media adjustment groups exceeded 100, further regression
analyses were performed for each group for each analyte. A total of 24 analytes met this
criterion (Table 3-19). Although quality of model fits differed by test media adjustment
group for each analyte , a significant fit was obtained for at least one group within each
analyte. In addition, although a significant model fit had been obtained for all analytes with
n>100 when test media adjustment groups where pooled (Table 3-15), better model fits
(e.g., higher r 2 values) were obtained for at least one test media adjustment group within
each analyte, except for chromium (Table 3-16).
F-tests (Draper and Smith 1981) were performed to compare regression results among the
four test media adjustment groups and among wet/dry sediment or the presence/absence
of salinity adjustment. Differences were considered significant if p#0.05. A summary of the
results is presented in Table 3-17. Significant differences between regression models among
all four test media adjustment groups were observed for 47 of the 75 analytes detected in
sediments used for amphipod bioassays (Table 3-17). In addition, regression models for wet
vs. dry sediment differed significantly for 29 analytes; and 35 analytes differed significantly
by presence/absence of salinity adjustment.
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SECTION 3: ANALYSIS
Scatter plots associated with regression analyses for all chemicals, test media adjustment
groups, and data transformations for amphipods are presented in Appendix H. Additional
plots of exposure response results for selected compounds are presented in Figures 3-17
through 3-29.
Mussel (Mytilus edulis) Regression Analysis
Results of the Mytilus toxicity bioassay consisted of counts of individuals surviving and
counts of individuals displaying abnormal development. Because sample sizes were not
constant among replicates, all Mytilus effects data were expressed as the proportion of
individuals at the start of the bioassay. Proportions were arcsine-square root transformed
(Zar, 1984) prior to analyses to correct for non-normality of proportion data. The
independent variables consisted of untransformed and natural-log-transformed
concentrations of chemicals in pore water (µg/L). Simple linear regression analyses were
performed using SAS (1994) PROC REG. All models were considered significant if p#0.05.
Prior analyses indicated that Mytilus survival was poorly related to chemical concentrations
in pore water, regardless of whether data were untransformed or natural-log transformed.
Significant regression fits were obtained for only 10 of 46 compounds based on
untransformed data and for only 8 of 46 based on transformed data. Values for r 2 were low
for both approaches, ranging from 0.0058 to 0.1 for untransformed data and 0.0053 to
0.33 for transformed data. Due to the low quality of the relationship between Mytilus
survival and pore water concentrations, this analysis was not pursued further.
In contrast to Mytilus survival, the proportion of normal Mytilus was strongly related to
chemical concentrations. Significant model fits were obtained for 37 of 41 chemicals based on
untransformed data and 39 of 41 chemicals for transformed data (Table 3-18). The proportion
of normal Mytilus was negatively related to chemical concentration for all chemicals
evaluated. Among models for untransformed data, r 2 ranged from 0.029 (silver) to 0.84
(aldrin; Table 3-18). For models based on transformed data, r 2 ranged from 0.04 (4,4’-DDD) to
0.83 (4-nitrophenol, chrysene, high molecular weight PAHs, and 4-methylphenol; Table 3-18).
With the exception of eight compounds (aldrin, arsenic, barium, beryllium, chromium,
endrin aldehyde, total phenol, and vanadium), natural-log-transformed data explained more
variability in the proportion of normal Mytilus than did untransformed data (Table 3-18).
Although pore water used for the Mytilus toxicity tests was adjusted in a manner
comparable to the sediment used for the amphipod tests (e.g., derived from wet or dry
sediment, with or without salinity adjustment), because no relationship was found between
sediment concentrations and pore water concentrations (see below), regression models for
the four test media adjustment groups were not developed.
Scatterplots associated with regression analyses for all chemicals and data transformations
for Mytilus are presented in Appendix H. Additional plots of exposure-response results for
selected compounds are presented in Figures 3-30 through 3-38.
Estimated Effect Levels
In addition to determining which compounds best described effects observed in the toxicity
bioassays, regression models were used to estimate concentrations in sediment and pore
water that were associated with 20 and 50 percent lethality (i.e., LC 20 or LC 50 ) or effects (i.e.,
EC 20 or EC 50 ) concentrations. LC and EC values were only calculated for those chemicals
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SECTION 3: ANALYSIS
with samples sizes >15 for amphipods and >40 for Mytilus, for which regression slopes were
negative with significant (i.e., p 0.5)
and the largest sample sizes, followed by LC and EC values based on models with high r 2
and small sample sizes. Moderate uncertainty is associated with LC and EC values based on
models where 0.2< r 2 < 0.5. Due to the small amount of variation they describe, LC and EC
values based on models with r 2 < 0.2, regardless of sample size, are not recommended for
use in remedial decision-making.
The LC and EC values with the least amount of uncertainty were carried forward into the
stressor-response profile and are presented with other selected effects levels in Section 3.2.2.
Although only 20 and 50 percent effects levels were estimated, the simple linear regression
analyses and associated figures may also be used to estimate concentrations associated with
less severe effects on the test organisms. Additional levels (e.g., EC 10 ) also could be
calculated, but time constraints precluded including them in this draft. The chemical data
that had been used for the regression was then screened using as the derived EC 20 s and
EC 50 s and LC 20 s or LC 50 s to determine the final COPECs. The results of the screening are
presented in Table F-3 for sediment and Table F-4 for pore water.
3.2.1.4 Chemical Correlation Evaluation
Additional regression analyses were conducted to evaluate chemical factors that could
potentially affect the cumulative toxicity of COPECs to ecological receptors. These factors,
described in the following subsections, consisted of the following:
• Relationship of COPEC concentrations in pore water to those in sediment
• Co-occurrence of COPECs in sediment
• Principal components analyses in sediment
COPEC Concentration Relationship Between Sediment and Pore Water
For pore water bioassay data to aid in screening potential toxicity from sediments at Bolsa
Chica, the relationship between concentrations of COPECs in sediment to those in pore
water must be known. If pore water concentrations can be estimated based on sediment
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SECTION 3: ANALYSIS
concentrations, potential toxicity that may result following inundation of sediments that are
currently dry may be estimated, and remedial actions to mitigate this toxicity may be
planned.
Simple linear regression analyses of COPEC concentrations in pore water on those in
sediment were performed using SAS (1994) PROC REG. All models were considered
significant if p#0.05. The results of these analyses (scatterplots and associated regression
analyses) for all chemicals and data transformations are presented in Appendix H. Of
70 chemicals considered, significant regressions based on untransformed data were
obtained for only seven chemicals (aldrin, arsenic, beryllium, alpha chlordane, endosulfan
sulfate, mercury, and phenanthrene). The highest r 2 for these chemicals was 0.28. Significant
regression models were obtained for 10 of 70 chemicals (acenaphthene, aldrin, arsenic,
beryllium, alpha chlordane, copper, endosulfan I, endrin aldehyde, total DDT, and thallium)
based on natural-log-transformed data. The highest r 2 from these data was 0.24.
Because significant relationships between concentrations of COPECs in pore water to those
in sediment were observed for few chemicals, and these relationships generally accounted
for less that 25 percent of variation, the pore water bioassay results cannot be used to predict
potential toxicity from pore water associated with the sediments. The pore water bioassays
may, however, be used to evaluate potential toxicity at locations where pore water already
exists.
Correlations Between COPECs in Sediment
Many COPECs have been detected in sediment from throughout the Bolsa Chica Lowlands
(using the entire ERA Sampling and Analyses dataset). To aid in streamlining future data
collection, correlation analyses were performed among analytes detected in sediment to
determine which chemicals were consistently detected in association with each other.
Analyses for chemicals whose occurrence is highly correlated may be reduced, such that
only those chemicals that are the best indicators are analyzed for.
Correlation analyses were performed using SAS (1994) PROC CORR. The resulting
correlation matrix is presented in Table 3-22.
Principal Components Analyses for COPECs in Sediment
Principal components analyses (PCA), a multivariate statistical technique, is another
approach to reduce the dimensionality (i.e., number of variables) associated with COPECs in
sediment. PCA is a statistical technique that linearly transforms the original numerical
variables to a substantially smaller set of uncorrelated variables that represent most of the
information in the original dataset (Dunteman, 1989). These uncorrelated variables, known as
principal components, are a linear combination of the original variables and are sorted in
decreasing order of the amount of variability in the original dataset they explain. Backcorrelation
of the principal component scores with the original data provides an indication of
which parameters each principal component represents. PCA is generally a data evaluation
method used to explore underlying relationships among variables in a large dataset.
PCA was performed on the sediment data previously used for correlation analyses using
SAS (1994) PROC PRINCOMP. (Note: the complete output from the principal components
analyses is included in Appendix H.) A total of 47 principal components was generated, of
which the first 9 accounted for 79.5 percent of the variance in the sediment data (Table 3-23).
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SECTION 3: ANALYSIS
These nine primary principal components were back-correlated with the original variables
in the dataset (Table 3-24). The first principal component is highly correlated with
petroluem compounds (e.g., PAHs, TPH, waste oil, etc.) and may be interpreted as a
measure of petroleum contamination. The second principal component best correlates to
metals (nickel, vanadium, mercury, zinc, and lead) and total PCBs. The third component is
positively correlated to organochlorines and copper and negatively correlated to petroleum
compounds. Component 4 is negatively correlated to PAHs and positively correlated to
organochlorines and metals (Table 3-24). Component 5 is positively correlated to inorganics
and negatively correlated to organochlorines.
3.2.2 Stressor-Response Profile
The stressor-response profile presents the results of the stressor-response analysis. It results in
a set of reference toxicity values (RTVs) that were then used as the basis for estimating risks to
representative species at the Bolsa Chica Lowlands. The RTVs were selected primarily from
the site-specific dose-response information, in addition to other available sources, including
toxicological databases, wildlife toxicological reviews, and scientific literature.
The most conservative of the reliable RTVs generally were used, because of the stated future
land use (mitigation and wildlife refuge). The RTVs were selected according to a specified
hierarchy. This was presented for aquatic organisms (sediment and surface water exposure)
in Sections 2.3.3 and 3.2.2, and for terrestrial organisms in Section 3.2.2. The RTVs included
both acute and chronic effect levels. The selection of RTVs for the various receptor groups is
presented below. In addition, the GIS application and Tables 3-25 to 3-28 identify the RTVs
that were used in the risk calculations. RTVs representing no observed adverse effect levels
(NOAELs), NOECs, lowest observed adverse effect levels (LOAELs), or LOECs are
preferred over those for lethal doses or concentrations (such as LD 50 or LC 50 ).
The RTVs for terrestrial plants and invertebrates exposed to sediment/soil were obtained
from several sources, including wildlife toxicity reviews, literature searches, and toxicity
databases, such as PHYTOTOX and the database compiled by Efroymson et al. (1997a and
1997b). The RTVs are presented in Table 3-25 for terrestrial plants and in Table 3-26 for
terrestrial invertebrates.
The RTVs for birds and mammals exposed to sediment/soil and surface water were
obtained from several sources, including wildlife toxicity reviews, literature searches,
Health Effects Assessment Summary Tables (HEAST), Integrated Risk Information System
(IRIS), and toxicity databases, such as TERRETOX. The most conservative RTVs were
typically selected for terrestrial receptors with the following two additional criteria: Where
possible, a) values that were based on test species most similar to representative Bolsa Chica
species were selected, and b) sources reporting both a NOAEL and a LOAEL were generally
preferred. The RTVs are presented in Table 3-27 for birds and in Table 3-28 for mammals.
The RTVs for aquatic organisms (e.g., benthic macroinvertebrates) exposed to sediment
were obtained from the dose-response regression analyses conducted on the amphipod
survival and reburial bioassays and Nereis bioaccumulation studies described in the
previous section. The ER-L and ER-M values from Long et al. (1995), and Long and Morgan
(1990) where not available in Long et al. (1995), are also included as reference benchmarks.
RTVs obtained from Long and Morgan (1990) include 4,4’-DDD, 4,4’-DDT, chlordane, and
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SECTION 3: ANALYSIS
dieldrin. These values do not have as high a degree of confidence as those obtained from
Long et al., 1995 because of limited sample size. The RTVs for sediment are presented in
Table 3-29.
The RTVs for aquatic organisms (e.g., invertebrates and fish) exposed to surface water were
obtained from the California Water Quality Standards (U.S. EPA, 2000), as well as sitespecific
bioassay using topsmelt, Ceriodaphnia, and Mysidopsis (described in the previous
section). In addition, RTVs for aquatic plants exposed to surface water are presented. The
RTVs for surface water are presented in Table 3-30.
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SECTION 4
Risk Characterization
The Risk Characterization is the final step in the ERA process whereby evidence linking
COPECs to potential adverse ecological effects in the Lowlands is evaluated using both
quantitative and qualitative methods. This evaluation is completed through the integration
of information gathered in the Problem formulation with the results of the Analysis – the
Exposure Characterization and the Ecological Effects Characterization – to establish a
“weight-of-evidence” for potential risk. For this ERA, the evidence evaluated consisted of
measured chemical concentrations in abiotic and biotic media, exposure estimates for birds
and mammals, results of site-specific toxicity bioassays and bioaccumulation studies for
aquatic organisms, and toxicity information obtained from the literature. In addition, the
proposed restoration plan for the different evaluation areas in the Lowlands was considered
in the overall assessment of risk potential to ecological receptors. The characterization of
risk is accomplished through three interrelated steps: risk estimation, risk description, and
uncertainty analysis. The final product is a listing of COECs for the Lowlands that will be
recommended for further evaluation or remedial action.
The identification of COECs through the Risk Characterization process is presented in
Figure 4-1. All COPECs that exceeded any available RTV as well as chemicals that showed
significant bioaccumulation in Nereis clam worms were retained as COECs. The overall risk
posed by a COEC in a given medium and evaluation area was determined based on the
types of RTVs that were exceeded (i.e., no-effect levels vs. low-effect levels and chronic
effect levels vs. acute effect levels). The overall risk categories were defined as follows:
• Unknown – RTVs were not available, so risk could not be quantified.
• None – Exposure does not exceed any of the available RTVs.
• Uncertain – Exposure exceeds a no-effect level, but risk could not be fully quantified
because a low-effect level was not available (Category U).
• Some Possible Risk – Exposure exceeds a no-effect level, but not a chronic low-effect
level (Category C).
• Possible Risk – Exposure exceeds a chronic low-effect level, but not an acute effect level
(Category B).
• Probable Risk – Exposure represents the highest level that could be quantified. Exposure
exceeds an acute effect level or showed significant bioaccumulation in Nereis clam
worms (Category A).
4.1 Risk Estimation
The risk estimation focuses primarily on quantitative methods to evaluate the potential for
risk. For this ERA, these included numerical estimates of risk, or hazard quotients (HQs),
and evaluation of site-specific toxicity bioassays and bioaccumulation studies.
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SECTION 4: RISK CHARACTERIZATION
Hazard quotients were developed for two types of comparisons using the indicated equation:
1. Direct comparisons of measured concentrations to media-based effect concentrations
(RTVs) of COPECs in abiotic media. These comparisons were conducted for terrestrial
plants and invertebrates, aquatic plants and benthic macroinvertebrates, and fish.
⎛ Exposure concentration ( mg / kg or mg / L)
HQ =
⎜
⎝ RTV ( mg / kg or mg / L)
⎞
⎟
⎠
2. Comparisons of estimated exposure dosages via the food chain uptake model to effects
dosages (RTVs). These comparisons were conducted for birds and mammals.
⎛ Exposure dosage ( mg / kgbw / d)
HQ =
⎜
⎝ scaled RTVw ( mg / kgbw / d)
⎞
⎟
⎠
The species scaled RTV (or RTV w ) was developed using allometric body weight scaling
methods presented in Sample, et al. (1996) and Sample and Arenal (1999). The scaling
factors applied were of 1.2 and 0.94 for birds and mammals, respectively (Sample and
Arenal, 1999):
where:
RTV
w
⎛ BWt
⎞
= RTVt
⎜
BW
⎟
⎝ w ⎠
RTV t = the RTV for a test species (Tables 3-27 and 3-28)
BW t and BW w = the body weights (in kg) for the test and wildlife species,
respectively, and
b = the class-specific allometric scaling factor.
As depicted in Figure 4-1, the exposure point concentration for each COPEC was compared
to chronic no-effect levels, chronic low-effect levels, and acute-effect levels (where available)
as RTVs for all effects levels were not identified for all receptor groups. Typically, if chronic
no-effect or low-effect levels were available, then acute-effect levels were not identified. One
exception was the values obtained from the California Water Quality Standards (U.S. EPA,
2000), in which both acute and chronic low-effect levels were reported. In general, RTVs for
terrestrial receptors were limited to chronic no-effect and low-effect levels. RTVs for aquatic
receptors included both chronic and acute effect levels. As described in Section 3.1.4.2, the
exposure point concentrations selected for each receptor group were either the maximum
detected value or the 95 th UCL. For some chemicals, the maximum detected value was less
than ½ the maximum non-detect value and the risks were calculated using the ½ non-detect
value (these are flagged with an asterix in the risk tables 4-1 through 4-4). The risk estimates
for each receptor group are presented in the following subsections for each evaluation area
in the Lowlands. As noted earlier (Section 1), the evaluation areas were identified based on
Cells that either currently have or will have similar habitats after the proposed restoration is
completed. These evaluation areas were presented previously, but are listed below for
reference:
1−b
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SECTION 4: RISK CHARACTERIZATION
• Bolsa Bay – Inner Bolsa Bay (Cell IB) and Outer Bolsa Bay (Cell OB)
• Full Tidal – Cells 1, 1A, 3 through 8, 15 through 18, 43, 44, 51, 58, 59, 61, and 62
• Future Full Tidal – Cells 14, 19 through 40, and 63
• Garden Grove – Winterburg Flood Control Channel – Cell 52
• Gas Plant Pond Area – offsite areas downgradient from the former gas plant, south of
Cells 11 and 12
• Muted Tidal plus Rabbit Island – Cells 41, 42, 45 through 50, 53, 55, 60, 66, and 67
• Seasonal Ponds – Cells 2, 9 through 13
The receptors evaluated for terrestrial (e.g., upland) exposures consisted of terrestrial plants
and invertebrates, Belding’s savannah sparrow (or “sparrow”), American kestrel (or
“kestrel”), western harvest mouse (“mouse”), and coyote (“coyote”). Evaluation areas within
the Lowlands that were assessed for potential risks to terrestrial receptors included Future
Full Tidal, Gas Plant Pond Area, Muted Tidal plus Rabbit Island, and Seasonal Ponds.
The receptors evaluated for aquatic and semi-aquatic exposures consisted of aquatic plants,
invertebrates, and fish; black-crowned night-heron (or “heron”); black-necked stilt (“stilt”);
and least tern (or “tern”). The evaluation areas within the Lowlands that were assessed for
potential risks to aquatic and semi-aquatic receptors included Bolsa Bay, Full Tidal, Future
Full Tidal, Garden Grove-Wintersburg Flood Control Channel, Gas Plant Pond Area, Muted
Tidal plus Rabbit Island, and Seasonal Ponds.
4.1.1 Sediment /Soil – Terrestrial Receptors
Sediment/soil from evaluation areas identified above as terrestrial habitat were evaluated
for potential risks to terrestrial receptors. Risk estimates were calculated for terrestrial plants
and invertebrates, as well as upland birds, and mammals. The results for chemicals with
HQs exceeding 1 are presented in Table 4-1 for plants and invertebrates and in Table 4-2 for
birds and mammals. The HQs for all detected chemicals are presented in Appendix I,
Tables I-1 and I-2.
4.1.1.1 Future Full Tidal
Terrestrial Plants
Terrestrial plants were quantitatively evaluated through comparison to RTVs from literature
sources (Table 3-25) as site-specific toxicity values were not derived for terrestrial plants.
Chronic NOECs were only available for a limited number of COPECs, so most of the
comparisons were conducted using chronic LOECs. A summary of HQs exceeding one for
terrestrial plants is presented in Table 4-1. Two chemicals, nickel and selenium, exceeded
chronic NOECs with HQs of 650 and 384, respectively. Comparisons to chronic LOECs
resulted in 17 inorganics and 4 organics posing a possible risk (Category B). The HQs
ranged from 1.9 for 4-nitrophenol to 850 for lead. Of those chemicals exceeding chronic
LOECs, 4 were evaluated using an exposure point concentration that was ½ the reporting
limit for a non-detect.
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SECTION 4: RISK CHARACTERIZATION
Terrestrial Invertebrates
Terrestrial invertebrates were quantitatively evaluated through comparison to RTVs from
literature sources as site-specific toxicity values were not derived (Table 3-26). Similar to
plants, most RTVs available were for chronic LOECs and only a few chronic NOECs were
used. Risk estimates for terrestrial invertebrates (Table 4-1) indicated that cadmium (HQ=19)
and zinc (HQ=116) exceeded chronic NOECs. Chronic LOECs were exceeded by 11 inorganic
and 7 organic chemicals indicating a possible risk (Category B) for these COECs. The HQs
ranged from 1 to 565; vanadium (HQ=565), mercury (HQ=380), and chromium (HQ=313)
had the highest HQs. Of those chemicals exceeding chronic LOECs, 2 were evaluated using
an exposure point concentration that was ½ the reporting limit for a non-detect.
Upland Birds
Birds were evaluated quantitatively through comparison of estimated total daily dosages to
chronic NOAEL and LOAEL RTVs obtained from the literature (Table 3-27). Site-specific
toxicity values and acute toxicity values were not obtained for birds. Two upland bird
species were used for screening at the Future Full Tidal including sparrow and kestrel
(Table 4-2). Sparrows were more sensitive to chemical concentrations (i.e., had a higher HQ)
than kestrels. Six metals exceeded NOAELs and two, lead and zinc, also exceeded LOAELs.
LOAELs were not available for barium, chromium and vanadium so resulting risk to these
chemicals is uncertain (Category U). Some possible risk (Category C) is posed by cobalt for
both receptors and lead and zinc for kestrels because the LOAEL was not exceeded. Lead
and zinc pose a possible risk (Category B) to sparrows because both the NOAEL and
LOAEL were exceeded. NOAEL-based HQs ranged from 1.1 for barium (sparrow) to 13 for
lead (sparrow). LOAEL-based HQs for sparrows were 1.4 for lead and 1.01 for zinc.
Mammals
Mammals were quantitatively evaluated in a similar manner as birds, with the harvest
mouse and the coyote as representative species of mammals using the Future Full Tidal area
(Table 4-2). Inorganics were the only COECs for these receptors. The potential risk was
uncertain (Category U) for cobalt and vanadium because LOAELs were not available. There
is some possible risk (Category C) from exposure to barium and lead because the LOAELs
were not exceeded. The highest NOAEL HQ was 69 for barium (mouse).
4.1.1.2 Gas Plant Pond Area
Terrestrial Plants
COPECs detected in the Gas Plant Pond Area that exceeded available chronic NOECs for
terrestrial plants consisted of selenium and nickel with HQs of 11 and 1.7, respectively
(Table 4-1). Chronic LOECs were exceeded by 11 chemicals indicating a possible risk
(Category B). Of these chemicals, arsenic (HQ=41), benzo(g,h,i) perylene (HQ=23), and
benzo(a)pyrene (HQ=21) had the highest HQs. Of those chemicals exceeding chronic
LOECs, 5 were evaluated using an exposure point concentration that was ½ the reporting
limit for a non-detect.
Terrestrial Invertebrates
Available chronic NOECs for terrestrial invertebrates were not exceeded, but arsenic, chromium,
copper, vanadium, and acenaphthene all exceeded chronic LOECs indicating a possible risk to
terrestrial invertebrates from these COECs. HQs ranged from 1.1 to 3.8 (Table 4-1).
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SECTION 4: RISK CHARACTERIZATION
Upland Bird
Evaluations for upland bird receptors (Table 4-2) indicated that there was some possible risk
(Category C) to arsenic, cobalt, lead, and zinc; and uncertain risk (Category U) for
chromium and selenium. Sparrows were more sensitive and had NOAEL HQs ranging from
1.4 (arsenic) to 7.2 (chromium).
Mammals
Evaluations for mammals in the Gas Plant Pond Area (Table 4-2) indicated that arsenic
poses a possible (Category B) risk, and barium, lead, and zinc pose some possible risk
(Category C). Chemicals that exceeded NOAELs, but did not have LOAELs (Category U
risk) included cobalt, selenium, and vanadium. NOAEL HQs were typically higher for the
mouse and ranged from 2.7 (cobalt) to 37 (barium). NOAEL HQs for coyotes ranged from
1.3 (zinc) to 3.5 (barium). In addition to the inorganic COECs, dieldrin also showed some
possible risk to coyotes (HQ=1.9).
4.1.1.3 Muted Tidal Plus Rabbit Island
Terrestrial Plants
Evaluations for terrestrial plants (Table 4-1) indicated that both nickel and selenium
exceeded chronic NOECs with HQs of 5 and 8.4, respectively. Chemicals exceeding chronic
LOECs included 14 inorganics and 3 organics with HQs ranging from 1 for cadmium to
480 for lead. These chemicals are considered to pose a possible risk to terrestrial plants
(Category B). Of those chemicals exceeding chronic LOECs, 4 were evaluated using an
exposure point concentration that was ½ the reporting limit for a non-detect.
Terrestrial Invertebrates
Estimates of potential risks to terrestrial invertebrates (Table 4-1) indicated that risk for zinc
was uncertain because it exceeded a chronic NOEC (HQ=1.4), but a LOEC was not available.
Eight other inorganics and 1 organic posed a possible risk based on exceedance of a chronic
LOEC. HQs for these chemicals ranged from 1.3 to 34, with barium (HQ=34) and lead
(HQ=19) showing the greatest potential for risk.
Upland Birds
Evaluations for upland birds showed that lead posed possible risk (Category B) to the
sparrow with a NOAEL HQ of 14 and a LOAEL HQ of 1.4 (Table 4-2). Cobalt and zinc
posed some possible risk to upland birds, and chromium posed an uncertain risk to
sparrows. NOAEL HQs ranged from 1.3 for zinc (kestrel) to 14 for lead (sparrow).
Mammals
Risk estimates for the harvest mouse and the coyote (Table 4-2) indicated that barium and
lead posed some possible risk (Category C) to the mouse with HQs of 20 and 5, respectively.
Barium was the only COEC identified for coyotes. Chemicals with uncertain risk (Category
U) included cobalt and vanadium.
4.1.1.4 Seasonal Ponds
Terrestrial Plants
Evaluations for terrestrial plants (Table 4-1) showed that nickel and selenium exceeded chronic
NOECs with HQs of 10 and 11, respectively. Chemicals that exceeded chronic LOECs (possible
risk – Category B) included 12 inorganics and 2 organics. HQs ranged from 2.1 for molybdenum
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SECTION 4: RISK CHARACTERIZATION
to 160 for arsenic. Of those chemicals exceeding chronic LOECs, 4 were evaluated using an
exposure point concentration that was ½ the reporting limit for a non-detect.
Terrestrial Invertebrates
Comparisons for terrestrial invertebrates (Table 4-1) show that chronic NOECs were
exceeded by zinc with an HQ of 1.1, but risk is considered uncertain because a chronic
LOEC was not identified. Chemicals exceeding chronic LOECs consisted of 6 inorganics and
1 organic indicating possible risk (Category B) for these COECs. Those with the highest HQs
included arsenic, barium and chromium, with respective HQs of 5, 45, and 7.8.
Upland Birds
Risk estimates for upland bird species (Table 4-2) indicated that arsenic, cobalt, lead, and
zinc all posed some possible risk to sparrows (Category C). Chromium posed an uncertain
risk (Category U) because a LOAEL was not available). Zinc was the only chemical that
exceeded a NOAEL for kestrels indicating some possible risk (Category C).
Mammals
Risk evaluations for mammals (Table 4-2) indicated that barium and lead posed some
possible risk (Category C) for the mouse and coyote (barium only). Cobalt and vanadium
also posed an uncertain risk (Category U) for the mouse. The NOAEL HQ ranged from
1.2 or lead (mouse) to 52 for barium (mouse). None of the chemicals detected exceeded
available LOAELs.
4.1.2 Sediment/Soil – Aquatic and Semi-Aquatic Receptors
Areas of the Lowlands that were evaluated for potential risks to aquatic and semi-aquatic
receptors consisted of Bolsa Bay, Full Tidal, Future Full Tidal, Garden Grove-Wintersburg
Flood Control Channel, Gas Plant Pond Area, Muted Tidal plus Rabbit Island, and Seasonal
Ponds. Risk estimates were calculated for aquatic plants, aquatic invertebrates, and semiaquatic
birds (heron, stilt, and tern). The results for chemicals with HQs exceeding 1 are
presented in Table 4-1 for aquatic plants, Table 4-3 for aquatic invertebrates, and Table 4-2
for semi-aquatic birds. The HQs for all detected chemicals are presented in Appendix I,
Tables I-1, I-2, and I-3.
It should be noted that although the sediment bioaccumlation studies using Nereis showed
significantly (P

SECTION 4: RISK CHARACTERIZATION
selenium exceeded both chronic NOECs and chronic LOECs. Chemicals exceeding chronic
LOECs included 10 inorganics and 2 organics. The overall risk for these chemicals is
considered to be possible (Category B). All HQs for excceedances of chronic LOECs were
less than 10. Arsenic (HQ=5.5) and lead (HQ=5.5) had the highest HQs. Of those chemicals
exceeding chronic LOECs, only one was evaluated using an exposure point concentration
that was ½ the reporting limit for a non-detect.
Aquatic Invertebrates
Aquatic invertebrates were evaluated using all levels of RTVs including chronic no-effects
(NOECs), chronic low-effects (ER-L and LC20s), and acute effects (ER-M and LC 50 ).
Chemicals that exceeded at least one effect level are presented in Table 4-3.
Chemicals with the highest level of risk (Category A- probable) exceeded either the ER-M
and/or LC 50 amphipod test values. These included the inorganic chemicals, nickel, selenium,
and thallium (HQs ranging from 1.7 to 2.7). Among the organics, the ER-M was exceeded for
six chemicals: 4,4’-DDD, 4,4’-DDE, chlordane (technical, alpha, and gamma), and total DDT,
with HQs ranging from 1.8 (4,4’-DDD) to 43 (chlordane-technical). The LC 50 was exceeded by
di-n-octylphthalate, TPH diesel, waste oil, and combined TPH diesel plus waste oil. The HQs
for these chemicals ranged from 2.3 (di-n-octylphthalate) to 4.2 (TPH diesel).
Possible risks (Category B) in which the chemical concentration exceeded a chronic loweffect
level (i.e., ER-L or the LC 20 value for amphipod toxicity) were observed for a number
of inorganic and organic parameters, as follows. Inorganics that exceeded the ER-L included
arsenic, cadmium, copper, lead, nickel, and zinc, with HQs ranging from 1.1 to 6.7. Organics
exceeding the ER-L included 4,4’-DDD, 4,4’-DDE, 4,4’-DDT, chlordane (technical, alpha, and
gamma), dieldrin, total DDT, and total PCBs. HQs among this group were generally higher
than for the inorganics (ranging from 1 to 520). Inorganic chemicals exceeding the LC 20
included beryllium, chromium, cobalt, nickel, selenium, thallium, vanadium, and zinc (HQ
ranging from 1.3 to 7.1). Organics exceeding the LC 20 included beno(b)fluoranthene,
di-n-octylphthalate, oil and grease, phenanthrene, TPH diesel, waste oil, combined
TPH diesel plus waste oil, low molecular weight (MW) PAHs, and total PAHs. HQ for
these exceedances ranged from 1 to 51 (TPH diesel).
A small number of chemicals showed some possible risk (Category C) including silver,
anthracene, benzo(a)anthracene, benzo(a)pyrene, chrysene, fluoranthene, pyrene, and high
MW PAHs with HQs ranging from 1.1 to 52 (fluoranthene).
A large number of chemicals resulted in uncertain risks (Category U) because low-effect
levels were not available. HQs for these chemicals ranged from 1.1 to 27. The potential for
risk to these chemicals may be overestimated since they were compared to the Nereis NOEC,
but they did not have a low-effect level available.
Two toxicity bioassays were conducted with sediment collected from Bolsa Bay. The tests
were conducted using the marine amphipod (Eohaustorius estuarius). Neither sample was
toxic, and results were not statistically different from controls for survival and reburial.
Two sediment bioaccumulation studies were conducted using the clam worm Nereis viriens.
None of the samples were significantly different from controls for survival, but barium,
nickel, and 4,4’-DDE showed significantly increased levels of bioaccumulation in worms
SAC/143368(004.DOC) 4-7 ERA REPORT
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SECTION 4: RISK CHARACTERIZATION
tested in sediment collected from Outer Bolsa Bay. 4,4’-DDE also showed significantly
increased bioaccumulation in worms tested in Inner Bolsa Bay sediments.
Semi-Aquatic Birds
Semi-aquatic birds used to estimate risks included the heron, stilt, and tern (Table 4-2). The
tern was the most sensitive receptor (e.g., highest HQs) followed by the heron and then stilt.
Chemicals that showed the highest risk (Category B) included cobalt and Aroclor 1254 for
the tern; and copper, lead, zinc, and 4,4’-DDE for both heron and tern. NOAEL HQs for
these chemicals ranged from 1.4 for copper (heron) to 91 for zinc (tern). The LOAEL HQs
ranged from 1.1 for copper (heron) to 10 for zinc (tern). Two chemicals, cobalt (heron) and
lead (stilt), showed some possible risk (Category C) since they exceed NOAELs, but not
LOAELs. Several chemicals (including chromium, selenium, vanadium, and dieldrin)
showed uncertain risk since they exceeded a NOAEL, but there was not a LOAEL available
to fully quantify the risks. The NAOEL HQs for these chemicals ranged from 1.0 for
vanadium (heron) to 54 for chromium (tern).
4.1.2.2 Full Tidal
Aquatic Plants
Estimates of potential risk to aquatic plants (Table 4-1) in sediments of the Full Tidal area
indicated that risks are primarily as a result of metals and PAHs. Nickel and selenium
exceeded both chronic RTVs with HQs of 8 and 380, respectively, for chronic NOECs and 3.2
and 127, respectively, for chronic LOECs. There were 16 chemicals that exceeded chronic
LOECs, indicating a possible risk to aquatic plants (Category B). The highest HQs were
observed for barium (HQ=23), benzo(a)pyrene (HQ=18), and benzo(g,h,i)perylene. Of those
chemicals exceeding chronic LOECs, 5 were evaluated using an exposure point
concentration that was ½ the reporting limit for a non-detect.
Aquatic Invertebrates
Evaluations for aquatic invertebrates (Table 4-3) showed that there were 6 inorganic
chemicals and 20 organic chemicals with probable risk (Category A). These chemicals
exceeded acute toxicity levels, as represented in Table 4-3 by the ER-M and LC 50 amphipod
test values. The chemicals that exceeded both the ER-M and LC 50 consisted of nickel,
fluorene, phenanthrene, and low MW PAHs. The HQs resulting from comparisons to LC 50 s
tended to be higher than were observed for comparisons to ER-Ms where both RTVs were
available for the same chemical. Overall, exceedances of ER-Ms resulted in HQs less than 10,
whereas HQs for LC 50 comparisons exceeded 10 for endrin ketone (54), fluorene (143), TPH
diesel (28), waste oil (14), and combined TPH diesel plus waste oil (16).
The low-effect levels (i.e., ER-L or the LC 20 value for amphipod toxicity) were exceeded for a
number of inorganic and organic chemicals. Those which did not have or exceed an acute
effect level (discussed above) were given an overall risk rating of possible risk (Category B).
This included 8 inorganics and 10 organics. The HQs for ER-L and LC 50 exceedances were
less than 10, with the exception of dieldrin with an ER-L HQ of 380.
There was only one chemical, fluoranthene, with some possible risk (Category C) since it
exceeded the NOEC, but not any of the low-effect levels. However, there were 18 chemicals
with uncertain risk (Category U) since they exceeded the Nereis toxicity NOEC, but did not
have a low-effect level available to fully quantify the risk.
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SECTION 4: RISK CHARACTERIZATION
Nine toxicity bioassays were conducted with sediment collected from the Full Tidal area,
primarily in Cells 1, 3, 8, and 51. The tests were conducted using the marine amphipod
(Eohaustorius estuarius) (Table 3-14). Two tests (from Cell 1 and from between Cell 3 and 8)
resulted in significantly reduced survival and reburial. One test (from Cell 3) resulted in
significant reduction in survival, but not reburial.
Seven sediment bioaccumulation tests were conducted using the clam worm Nereis viriens.
None of the samples were significantly different from controls for survival. However,
bioaccumulation for several chemicals was significantly increased including cobalt, nickel, and
vanadium from worms tested in Cell 3 sediments; and lead in worms tested in Cell 8 sediments.
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds indicated that terns were the most sensitive (Table 4-2).
Chemicals with possible risk (Category B) included cobalt, copper, zinc, and 4,4’-DDE for
terns, and zinc for herons. The NOAEL HQs for these chemicals ranged from 1.9 to 86, and
the LOAEL HQs ranged from 1.5 to 9.6 for copper and zinc, respectively. Chemicals with
some possible risk (Category C) included cobalt (heron) and lead (tern and heron).
Uncertain risks were estimated for several chemicals including barium, chromium,
selenium, and dieldrin. NOAEL HQs for these chemicals ranged from 1.0 for barium to
57 for chromium, both for terns.
4.1.2.3 Future Full Tidal
Aquatic Plants
Estimates of potential risk to aquatic plants in sediments of the Future Full Tidal area
indicated that risks are primarily a result of metals and PAHs. A summary of HQs
exceeding one for aquatic plants is presented in Table 4-1. Two chemicals, nickel and
selenium, exceeded chronic NOECs with HQs of 650 and 384, respectively. Comparisons to
chronic LOECs resulted in 17 inorganics and 4 organics posing a possible risk (Category B).
The HQs ranged from 1.9 for 4-nitrophenol to 850 for lead. Of those chemicals exceeding
chronic LOECs, 4 were evaluated using an exposure point concentration that was ½ the
reporting limit for a non-detect.
Aquatic Invertebrates
There were 14 inorganic and 28 organic chemicals with probable risk (Category A)
(Table 4-3). Chemicals that exceeded both the ER-M and LC 50 consisted of chromium, nickel,
zinc, chrysene, fluorene, phenanthrene, and low MW PAHs. Several chemicals had HQ
exceeding 100 for either the ER-M or the LC 50 . Chemicals with HQs greater than 100 from
comparisons to the ER-M included mercury (268) and chlordane – technical (633). Chemicals
with HQs greater than 100 for comparisons to the LC 50 included beryllium (133), cobalt
(181), nickel (224), thallium (276), and vanadium (193).
Chemicals with possible risk (Category B – exceedance of a chronic low-effect level, but not
an acute effect level) included anthracene, benzo(a)anthracene, benzo(a)pyrene,
benzo(b)fluoranthene, fluoranthene, pyrene, and high MW PAHs. The HQs for all these
chemicals were less than 10.
There were no chemicals in Category C (some possible risk), but there were several with
uncertain risk (Category U). These chemicals exceeded the NOEC, but did not have a loweffect
level RTV available. The NOEC HQs for these chemicals ranged from 44 to 1273.
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SECTION 4: RISK CHARACTERIZATION
Several toxicity bioassays were conducted using sediment collected from the Future Full
Tidal area, including Cells 14 and 23 (4 samples); Cell 21 (3 samples); Cells 28, 36, 37, 40, and
63 (1 sample each); Cells 30, 32, 38 (2 samples each). The tests were conducted using the
marine amphipod (Eohaustorius estuarius) (Table 3-14). All samples were significantly
different from controls for survival with the exception of three samples from Cell 14; one
sample from Cells 23, 32, 36, and 38; and two samples from Cell 34. In addition, one sample
from Cell 30 was also significantly different from controls for reburial.
Nine sediment bioaccumulation studies were conducted using the clam worm Nereis viriens.
None of the samples were significantly different from controls for survival, but several
showed significantly increased levels of specific chemicals, as shown below:
• Cell 21- 4,4’-DDD, 4,4’-DDE, acenaphthene, chrysene, and fluorene.
• Cell 23 – 4,4’-DDD and BHC-beta
• Cell 24 – copper and 4,4’-DDD
• Cell 30 – barium, copper, and lead
• Cell 34 – copper
• Cell 38 – copper, mercury, selenium, vanadium, zinc, 4,4’-DDD, and chlordane (alpha-,
gamma-, and technical)
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds (Table 4-2) indicated that herons were more sensitive
than terns in some instances, whereas terns were more sensitive in others. The differences
are accounted for by differences in dietary composition and the concentrations found in
various dietary components. Chemicals that herons showed more sensitivity to included
barium, chromium, cobalt, copper, nickel, and selenium. Terns were more sensitive to
cadmium, lead, mercury, vanadium, zinc, 4,4’-DDD, 4,4’-DDE, dieldrin, and Aroclor 1254.
Chemicals that had possible risks (Category B) included cobalt, copper, lead, zinc, 4,4’-DDE,
and Aroclor 1254. The NAOEL HQs for these chemicals ranged from 1.6 (copper) to 81
(zinc), both for terns. The LOAEL HQs ranged from 1.2 (copper) to 9.0 (zinc) for terns.
Chemicals with some possible risk (Category C) included cadimium (tern), and cobalt and
lead (stilt). Several chemicals had uncertain risks (Category U) including barium, chromium,
mercury, nickel, selenium, vanadium, 4,4-DDD, and dieldrin.
4.1.2.4 Garden Grove-Wintersburg Flood Control Channel
Aquatic Plants
Estimates of potential risk to aquatic plants in sediments (Table 4-1) of the Garden Grove-
Wintersburg Flood Control Channel indicated that risks are primarily due to metals and
PAHs. Nickel and selenium both exceeded chronic NOECs, but only selenium also exceeded
the LOEC indicating possible risk (Category B). Eight additional inorganics and 2 organics
also showed possible risk (Category B) by exceeding chronic LOECs. The highest HQs were
observed for benzo(a)pyrene (HQ=12) and benzo(g,h,i)perylene (HQ=10), both of which
were also evaluated using an exposure point concentration that was ½ the reporting limit
for a non-detect.
ERA REPORT 4-10 SAC/143368(004.DOC)
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SECTION 4: RISK CHARACTERIZATION
Aquatic Invertebrates
Acute effect levels (probable risk – Category A) were exceeded by 2 inorganic and 6 organic
chemicals (Table 4-3). The ER-M was exceeded by 4,4’-DDD, 4,4’-DDE, chlordane (technical),
chlordane-alpha, and total DDT. The HQs for these chemicals ranged from 1.2 to 3.6. The
LC 50 was exceeded by selenium, thallium, and phenanthrene with HQs ranging from 1 to 1.9.
Several chemicals showed possible risk (Category B) including 8 inorganics and 11 organics.
The HQs for all these chemicals are less than 10. Both the ER-L and LC 20 were exceeded by
nickel. Copper, lead, mercury, chlordane-gamma, and dieldrin exceeded the ER-L but not
the LC 20 with HQs ranging from 1.0 (copper) to 60 (dieldrin). Beryllium, cobalt, thallium,
vanadium, zinc, and 10 of the 11 organics exceeded the LC 20 but not the ER-L. HQs among
this group ranged from 1.2 (vanadium) to 11 (for selenium).
Several chemicals had some possible risk (Category C) or uncertain risk (Category U).
Category C chemicals included 3 metals and 5 organics which were all PAHs. The NOEC
HQs for these chemicals ranged from 2.3 (chrysene) to 71 (benzo(a)anthracene. The
Category U chemicals had NOEC HQs ranging from 3.5 (barium) to 100
(indeno(1,2,3-cd)perylene.
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds (Table 4-2) indicated that metals and pesticides pose
the greatest potential for adverse effects. Terns were the most sensitive receptor with the
exception of exposure to barium and cadmium for which the heron was more sensitive. As
noted previously for the Future Full Tidal area, this is due to differences in concentrations of
chemicals present in site-collected biota and the differences in dietary composition between
the two receptors. Chemicals that showed possible risk (Category B) included cobalt,
copper, lead, zinc, 4,4’-DDE, for both herons and terns as well as Aroclor 1254 for terns. The
NOAEL HQs for these chemicals ranged from 1.9 for copper (heron) to 286 for zinc (tern).
The LOAEL HQs ranged from 1.5 for copper (heron) to 858 for 4,4’-DDE (tern). Chemicals
with some possible risk (Category C) included cadmium for heron and tern, and cobalt and
lead for stilt. Several chemicals had uncertain risks (Category U) including barium,
chromium, selenium, vanadium, 4,4’-DDD, and dieldrin. The NOAEL HQs for these
chemicals ranged from 1.2 for chromium (stilt) to 300 for selenium (tern).
4.1.2.5 Gas Plant Pond Area
Aquatic Plants
Estimates of potential risk to aquatic plants in sediments of the Gas Plant Pond Area
indicated that risks are primarily a result of metals and PAHs (Table 4-1). COPECs detected
in the Gas Plant Pond Area that exceeded available chronic NOECs for aquatic plants
consisted of selenium and nickel with HQs of 11 and 1.7, respectively. Chronic LOECs were
exceeded by 11 chemicals indicating a possible risk (Category B). Of these chemicals, arsenic
(41), benzo(g,h,i) perylene (23), and benzo(a)pyrene (21) had the highest HQs. Of those
chemicals exceeding chronic LOECs, 5 were evaluated using an exposure point
concentration that was ½ the reporting limit for a non-detect.
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SECTION 4: RISK CHARACTERIZATION
Aquatic Invertebrates
There were 4 inorganic and 14 organic chemicals that showed probable risk (Category A) by
exceeding acute toxicity levels (Table 4-3). Chemicals that exceeded both the ER-M and the
LC 50 included fluorene, phenanthrene, and low MW PAHs. The HQs for these chemicals
ranged from 1.0 (phenanthrene) to 367 (fluorene). The HQs for comparisons to the ER-M
tended to be lower than those for comparisons to the LC 50 . The largest difference occurs
with fluorene, for which the ER-M HQ was 6.7 and the LC 50 HQ was 367. This indicates that
the LC 50 s for some chemicals may be overestimated depending on the availability of data.
The HQs for other chemicals exceeding either the ER-M or the LC 50 were all less than 10.
Possible risk (Category B), whereby the ER-L or the LC 20 value for amphipod toxicity was
exceeded, was observed for 9 inorganic and 5 organic chemicals. Both the ER-L and LC 20
were exceeded by nickel, zinc, and chrysene with HQs all below 2. The HQs for these
chemicals were comparable between the ER-Ls and LC 20 s. Other chemicals exceeding the
ER-L included copper, lead, mercury, silver, 4,4’-DDE, benzo(a)anthracene, and dieldrin
with HQs ranging from 1.1 (silver) to 105 (dieldrin). Other chemicals exceeding the LC 20
consisted of beryllium, cobalt, and benzo(b)fluoranthene with HQs ranging from 1.4 (cobalt)
to 7.1 (benzo[b]fluoranthene).
Some possible risk (Category C) was observed for cadmium, benzo(a)pyrene, fluoranthene,
pyrene, and high MW PAHs. These were all based on exceeding the no-effect level (Nereis
NOEC), but not a low-effect level. The HQs for these chemicals ranged from 2.3 (high MW
PAHs) to 102 (fluoranthene). Similarly, several chemicals (1 inorganic and 8 organics)
showed uncertain risk (Category U) since the Nereis NOEC was the only RTV available.
Three toxicity bioassays were conducted using the marine amphipod (Eohaustorius estuarius)
with sediment collected from the ponds downgradient from the former Gas Plant
(Table 3-14). Two samples were significantly different from controls for survival. None were
significantly different for reburial.
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds indicated that metals and pesticides pose the greatest
potential for adverse effects (Table 4-2). The tern was the most sensitive receptor in most
cases followed by the heron. Herons were more sensitive to arsenic and equally sensitive to
cadmium. The stilt was the least sensitive, with only one exceedance for chromium.
Chemicals with possible risk (Category B) consisted of cobalt, copper, lead, zinc, 4,4’-DDE,
and Aroclor 1254 (heron and tern). The NOAEL HQs for these chemicals ranged from 2.9 for
copper (heron) to 318 for zinc (tern). The LOAEL HQs ranged from 1.1 for Aroclor 1254
(heron) to 184 for 4,4’-DDE (tern). Two chemicals, arsenic (heron) and cadmium (heron and
tern), showed some possible risk (Category C), and several chemicals showed uncertain
risks (Category U). The NOAEL HQs for the Category U chemicals ranged from 1.4 for
chromium (stilt) to 663 for selenium (tern).
4.1.2.6 Muted Tidal plus Rabbit Island
Aquatic Plants
Potential risks to aquatic plants were estimated through comparison to RTVs for terrestrial
plants (Table 4-1). Calculation of HQs indicate that potential risks are primarily as a result of
metals and PAHs. Both nickel and selenium exceeded chronic NOECs for aquatic plants
ERA REPORT 4-12 SAC/143368(004.DOC)
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SECTION 4: RISK CHARACTERIZATION
with HQs of 5 and 8.4, respectively. Chemicals exceeding chronic LOECs included
14 inorganics and 3 organics with HQs ranging from 1 for cadmium to 480 for lead. These
chemicals are considered to pose a possible risk to terrestrial plants (Category B). Of those
chemicals exceeding chronic LOECs, 4 were evaluated using an exposure point
concentration that was ½ the reporting limit for a non-detect.
Aquatic Invertebrates
Evaluation of potential toxicity to aquatic invertebrates (Table 4-3) indicated that 9 inorganic
and 21 organic chemicals had probable (Category A) risk based on exceedance of an acute
RTV (ER-M or LC 50 ). Only two chemicals, nickel and zinc, exceeded both the ER-M and the
LC 50 . The HQs for these were similar between the two RTVs. All HQs for ER-M and LC 50
exceedances were less than 10 with the exception of lead (44), chlordane-technical (18), and
total PCBs (16) for ER-M and endrin aldehyde (14), endrin ketone (200), fluorene (32), TPHdiesel
(17), waste oil (13), and combined TPH-diesel plus waste oil (14 ) for the LC 50 .
Chemicals with possible risk (Category B) included 4 inorganics and 6 organics. Chrysene was
the only chemical that exceeded both the ER-L and LC 20 . Cadmium, mercury, anthracene,
benzo(a)anthracene, and naphthalene exceeded the ER-L but not the LC 20 . HQs among this
group ranged from 1.2 (benzo[a]anthracene) to 4.4 (mercury). Chemicals that exceeded the LC 20 ,
but not he ER-L included beryllium, vanadium, benzo(b)fluoranthene, and total PAHs. HQs
among this group ranged from 2.0 (vanadium) to 13 (benzo[b]fluoranthene).
Some possible risk (Category C) was estimated for silver, benzo(a)pyrene, fluoranthene,
pyrene, and high MW PAHs based on exceedance of the no-effect level (Nereis NOEC) but
not exceeding a low-effect level. The NOEC HQs for these chemicals ranged from 5.8 to 78.
Similarly, there were several chemicals that have uncertain risk (Category U) based on
exceedance of the Nereis NOEC. However, there was no other RTVs available for these
chemicals so the risk estimates may be overestimated.
Two toxicity bioassays were conducted using the marine amphipod (Eohaustorius estuarius)
with sediment collected from the Muted Tidal area (Table 3-14). One sample was significantly
different from controls for survival. Neither was significantly different for reburial.
Two sediment bioaccumulation studies were conducted using the clam worm Nereis viriens.
None of the samples were significantly different from controls for survival, but they were
significantly different for bioaccumulation of nickel in Cell 60, and lead and zinc in Cell 67.
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds indicate that metals and pesticides pose the greatest
potential for adverse effects (Table 4-2). The tern was the most sensitive receptor in all cases.
Chemicals with possible risk (Category B) included cobalt, lead, zinc, and 4,4’-DDE for both
heron and tern); and copper and Aroclor 1254 for tern. The NOAEL HQs for these chemicals
ranged from 3.5 for copper to 273 for lead, both for tern. The LOAEL HQs for these
chemicals ranged from 1.3 for cobalt (heron) to 80 for 4,4’-DDE (tern). Three chemicals
showed some possible risk (Category C), cobalt (stilt), copper (heron), and lead (stilt).
Several chemicals had uncertain risks (Category U) because although they exceeded the
NOAEL, LOAELs were not available. These included barium, chromium, selenium,
vanadium, 4,4’-DDD, 4,4’-DDT, and dieldrin. The NOAEL HQs for these chemicals ranged
from 1.1 for chromium (stilt) to 243 for selenium (tern).
SAC/143368(004.DOC) 4-13 ERA REPORT
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SECTION 4: RISK CHARACTERIZATION
4.1.2.7 Seasonal Ponds
Aquatic Plants
Potential risks to aquatic plants were estimated through comparison to RTVs for terrestrial
plants (Table 4-1). Calculation of HQs indicate that potential risks are primarily as a result of
metals and PAHs. Nickel and selenium exceeded chronic NOECs for aquatic plants with
HQs of 10 and 11, respectively. Chemicals that exceeded chronic LOECs (possible risk –
Category B) included 12 inorganics and 2 organics. HQs ranged from 2.1 for molybdenum
to 160 for arsenic. Of those chemicals exceeding chronic LOECs, 4 were evaluated using an
exposure point concentration that was ½ the reporting limit for a non-detect.
Aquatic Invertebrates
Evaluation of potential toxicity for aquatic invertebrates showed that there was probable
risk (Category A) for 7 inorganic 12 organic chemicals based on exceedance of an acute RTV
(Table 4-3). Nickel and phenanthrene exceeded both the ER-M and LC 50 . For chemicals
exceeding either the ER-M or the LC 50 , all of the HQs were less than 10 with the exception of
phenanthrene which had a LC 50 HQ of 20.
Possible risk (Category B) was observed for 6 inorganic and 10 organic chemicals that
exceeded either the ER-L or the LC 20 . Zinc and chrysene exceeded both the ER-L and LC 20 ,
and the HQs were fairly comparable between the two RTVs. The HQs for comparisons to
the ER-L and LC 20 were all less than 10 with the exception of benzo(b)fluoranthene (11) and
dieldrin (160).
Some possible risk (Category C) was observed for cadmium, pyrene, and high MW PAHs
based on exceedance of a no-effect level, but not a low-effect level. The NOEC HQs for these
chemicals ranged from 4.3 to 32.
Several chemicals had uncertain risk (Category U) because they exceeded the no-effect level,
but did not have a low-effect level. The NOEC HQs for these chemicals ranged from
1.1 (total phthalate esters) to 710 (phenol). The no-effect level was based on the Nereis NOEC
which has some uncertainty because no toxicity was observed in the bioassays. As such, the
HQs for these chemicals may be overestimated.
Seven toxicity bioassays were conducted using the marine amphipod (Eohaustorius estuarius)
with sediment collected from the Seasonal Ponds (Table 3-14). One sample was tested for
Cells 2 and 12, and five samples were tested from Cell 11. The samples from Cells 2 and 12,
as well as two samples from Cell 11, were significantly different from controls for survival.
None was significantly different for reburial.
Four sediment bioaccumulation studies were conducted using the clam worm Nereis viriens.
None of the samples was significantly different from controls for survival, but the samples
were significantly different for 4,4’-DDE and nickel in sediments tested from Cell 11.
Semi-Aquatic Birds
Risk estimates for semi-aquatic birds indicated that metals and pesticides pose the highest
potential for adverse effects (Table 4-2). Terns were the most sensitive receptor for all
chemicals with the exception of arsenic for which the heron was more sensitive. This was
primarily due to the intake from corixids which accounted for over 90% of the total
exposure. Chemicals that showed possible risk (Category B) included arsenic for heron;
ERA REPORT 4-14 SAC/143368(004.DOC)
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SECTION 4: RISK CHARACTERIZATION
cobalt, copper, lead, zinc, and 4,4’-DDE for both heron and tern; and arochlor 1254 for tern.
The NOAEL HQs for these chemicals ranged from 1.3 for copper (heron) to 220 for zinc
(tern). The LOAEL HQs ranged from 1.0 for copper (heron) to 91 for 4,4’-DDE (tern). Cobalt
and lead showed some possible risk to stilts, but had relatively low HQs. Several chemicals
had uncertain risks (Category U) including barium, chromium, nickel, selenium, vanadium,
4,4’-DDD, and dieldrin. The NOAEL HQs for these chemicals ranged from 1.1 for nickel
(tern) to 350 for selenium (tern).
4.1.3 Surface Water – Aquatic Receptors
Potential risks to aquatic receptors from exposure to surface water were evaluated using
several RTVs (Table 4-4) including California State acute and chronic standards (used for all
receptors - plants, invertebrates, and fish), established benchmarks (plants), and estimated
NOECs and LOECs from the site-specific bioassays conducted using aquatic invertebrates
and fish. In addition, the toxicity of surface waters to aquatic invertebrates and fish was also
measured using bioassays (Table 3-14), and is discussed with the estimated risks for each
area below.
4.1.3.1 Bolsa Bay
Aquatic Plants
Risk estimates for aquatic plants showed that only one chemical, dissolved copper, exceeded
any of the RTVs (Table 4-4). However, it showed probable risk (Category A) to plants
because it exceeded the acute California Water Quality Standard (CA-WQS).
Aquatic Invertebrates
Evaluations for aquatic invertebrates (Table 4-4) showed that dissolved copper had probable
risk (Category A) for exceedance of the acute CA-WQS. Four other inorganic and 2 organic
chemicals showed possible risk (Category B) because they exceeded the low-effect level
(Ceriodaphnia LOEC). The HQs for these chemicals ranged from 1.4 (dissolved cadmium) to
32 (sulfate). Chemicals with some possible risk (Category C) exceeded a no-effect level, but
not a low-effect level. The HQs for these chemicals ranged from 1.1 to 1.7.
Fish
Risk estimates for fish (Table 4-4) showed that dissolved copper had probable risk
(Category A), dissolved silver and dissolved zinc had some possible risk (Category C), and
dissolved beryllium and dissolved chromium had uncertain risk (Category U). The HQs for
all of these chemicals were close to 1.
Toxicity bioassays were conducted to evaluate toxicity to topsmelt using surface water
samples from Inner Bolsa Bay (Cell IB). The percentage of sample resulting in NOECs for
development, survival, and reproduction was 90.9 percent (the sample was adjusted for
salinity, so could not be tested at full strength). Because no adverse effects were seen in this
sample, the LOEC was greater than 90.9 percent.
4.1.3.2 Full Tidal
Aquatic Plants
Evaluation of potential risk to aquatic plants (Table 4-4) showed that only 4 chemicals were
of concern. Two, dissolved copper and endrin, have probable risk (Category A) to aquatic
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SECTION 4: RISK CHARACTERIZATION
plants. Dissolved copper exceeded no-, low-, and acute RTVs with the HQs of 7.8, 2.5, and
1.6 respectively. Endrin had HQs of 23 and 1.5 for the low-effect (chronic CA-WQS) and
acute CA-WQS, respectively. Two chemicals (dissolved nickel and dieldrin) had possible
risk (Category B) for exceeding the chronic CA-WQS.
Aquatic Invertebrates
Potential risks to aquatic invertebrates were probable (Category A) for dissolved copper and
endrin (Table 4-4). Several chemicals showed possible risks (Category B) with LOEC HQs
ranging from 1.1 (dieldrin) to 86 (sulfate).
Fish
Chemicals with probable risk (Category A) consisted of dissolved copper and endrin
(Table 4-4). Chemicals with possible risk were dissolved nickel and dieldrin, with CA-WQS
chronic HQs of 2.9 and 6.8, respectively. Dissolved arsenic, dissolved cadmium, dissolved
lead, and dissolved zinc showed some possible risk with NOEC HQs ranging from 1.0 (zinc)
to 3.3 (cadmium and arsenic).
Toxicity bioassays using topsmelt were conducted on surface water samples collected from
Cells 3 and 17 in the Full Tidal area. Neither sample was toxic to test organisms, but both
were adjusted for salinity and could not be tested at full strength. Percents of sample
resulting in NOECs for development, survival, and reproduction were 30.3 for Cell 3 and
73.2 for Cell 17. These were the highest concentrations of original sample tested. Because no
effects were seen, LOECs were greater than the tested concentrations.
4.1.3.3 Future Full Tidal
Aquatic Plants
Evaluations for aquatic plants (Table 4-4) indicated that copper (total and dissolved) could
have probable risks (Category A) for aquatic plants. The acute HQs were 3.1 and 2.7,
respectively. Chemicals with possible risk (Category B) consisted of arsenic, lead, nickel
(total and dissolved), zinc (total and dissolved), 4,4’-DDT, and dieldrin. The HQs for these
chemicals were less than 10 with the exception of 4,4’-DDT (13) when compared to the
chronic CA-WQS, and copper (15) and dissolved copper (13) when compared to the lowest
chronic value for plants.
Aquatic Invertebrates
Copper (total and dissolved) was the only chemical with probable risk to aquatic
invertebrates (Table 4-4). There were several chemicals with possible risk (Category B). The
LOEC HQs for these chemicals were less than 10 with the exception of arsenic (15), sulfate
(133), TPH-diesel (6,667) and waste oil (3,596).
Toxicity bioassays were conducted on surface waters collected from Cell 38 (Ceriodaphnia),
and Cell 36 (Mysidopsis). Bioassays using Ceriodaphnia were planned for the samples
collected from Cell 36, but given the total dissolved solids (electrical conductivity),
Mysidopsis were used instead. As such, the test waters were adjusted for salinity. Results of
the Ceriodaphnia tests found that samples were slightly toxic to test organisms. The
percentage of sample resulting in NOECs for reproduction, development, and survival was
50 percent and 100 percent for LOECs of reproduction, development, and survival. The EC 50
for reproduction was greater than 50 percent. The LC 50 was 57.4 percent. Mysidopsis
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SECTION 4: RISK CHARACTERIZATION
bioassays were not toxic to test organisms at the highest concentration tested, so NOECs
were 100 percent of the sample and the LOECs were greater than 100 percent.
Fish
Copper (total and dissolved) was the only chemical with probable risk to fish (Table 4-4).
Arsenic, lead, nickel, 4,4’-DDT, and dieldrin showed possible risk (Category B). The chronic
CA-WQS HQs for these chemicals were all less than 10 with the exception of 4,4’-DDT (13).
There were also several chemicals with some possible risk (Category C). The NOEC HQs
for these ranged from 1.0 (dissolved lead) to 6.3 (zinc). Chemicals with uncertain risks
(Category U) had fish NOECs less than 10 except for TPH-diesel (1,491) and waste oil (754).
Toxicity bioassays were conducted on surface waters collected from Cell 63 (topsmelt). The
bioassays using topsmelt resulted in no adverse effects on test organisms using 100 percent
sample. The NOEC was then 100 percent of sample and the LOEC was greater than
100 percent.
4.1.3.4 Garden Grove-Wintersburg Flood Control Channel
Aquatic Plants
Estimation of potential risks to aquatic plants showed that copper was the only chemical
that had a probable risk (Category A) with an acute CA-WQS HQ of 3.5 (Table 4-4). Possible
risk (Category B) was indicated for dissolved copper, nickel, zinc, and dieldrin. Dissolved
copper exceeded both the lowest chronic value for plants and the CA-WQS chronic value
with HQs of 4.7 and 1.5, respectively. Nickel (6.6) and dieldrin (52) also exceeded the CA-
WQS chronic level, but not the plant lowest chronic value. Zinc exceeded the plant lowest
chronic value, but not the CA-WQS chronic value.
Aquatic Invertebrates
Copper was the only chemical with probable risk to aquatic invertebrates (Table 4-4). There
were several chemicals with possible risk (Category B). The LOEC HQs for these chemicals
were less than 10 with the exception of 4-nitrophenol (23) and dieldrin (52). Arsenic (total
and dissolved), chromium, dissolved cobalt, and zinc all had some possible risk
(Category C). The NOEC HQs for these chemicals range from 1.4 (dissolved arsenic) to
45 (4-nitrophenol).
Toxicity bioassays were conducted with surface water collected from Cell 52. Given the total
dissolved solids (electrical conductivity), Mysidopsis were used instead of Ceriodaphnia. As
such, the test waters were adjusted for salinity. The results indicated that samples were not
toxic to organisms at the highest concentration tested; therefore, the NOEC was 100 percent
of the sample and the LOEC was greater than 100 percent of the sample.
Fish
Risk evaluations for fish indicated that copper was the only chemical with probable risk
(Category A) to fish (Table 4-4). Chemicals with possible risk included dissolved copper,
nickel, and dieldrin. The CA-WQS chronic HQs for these chemicals ranged from
1.5 (dissolved copper) to 52 (dieldrin). Cadmium, lead, and zinc showed some possible
risk (Category C) with fish NOEC HQs ranging from 2.9 to 6.7.
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SECTION 4: RISK CHARACTERIZATION
4.1.3.5 Gas Plant Pond Area
Aquatic Plants
Estimates of potential risk to aquatic plants (Table 4-4) indicated that there were no COPECs
that posed a risk to aquatic plants.
Aquatic Invertebrates
Evaluation of potential risk to aquatic invertebrates (Table 4-4) showed that TPH-diesel and
waste oil were the only COPECs that posed a risk. Both of these chemicals pose a possible
(Category B) risk based on exceedance of the LOEC for Ceriodaphnia.
Fish
Evaluation of potential risk to fish (Table 4-4) showed that TPH-diesel and waste oil were
the only COPECs that posed a risk. Both of these chemicals pose an uncertain risk (Category
U) because they exceeded the fish NOEC, but did not have any low-effect levels available.
4.1.3.6 Muted Tidal plus Rabbit Island
Aquatic Plants
Estimates of potential risk to aquatic plants (Table 4-4) indicated that there were no COPECs
that posed a risk to aquatic plants.
Aquatic Invertebrates
Evaluation of potential risk to aquatic invertebrates (Table 4-4) showed that TPH-diesel and
waste oil were the only COPECs that posed a risk. Both of these chemicals pose a possible
(Category B) risk based on exceedance of the LOEC for Ceriodaphnia.
Fish
Evaluation of potential risk to fish (Table 4-4) showed that were no COPECs that posed a
risk to fish.
4.1.3.7 Seasonal Ponds
Aquatic Plants
Estimates of potential risk to aquatic plants (Table 4-4) indicated that dissolved copper and
zinc pose a probable risk (Category A) to aquatic plants. Both exceeded the plant lowest
chronic value as well as the CA-WQS acute value (for which, the HQs were close to 1).
Copper and dissolved zinc pose a possible risk (Category B) with exceedances of the plant
lowest chronic value. The HQs for these chemicals were 1.5 and 2.8, respectively.
Aquatic Invertebrates
Evaluation of potential risk to aquatic invertebrates (Table 4-4) showed that dissolved
copper and zinc have probable risk (Category A). Several chemicals have possible risks
(Category B) to aquatic invertebrates. The LOEC HQs for these range from 1.4 (dissolved
cadmium) to 1,333 ( TPH-diesel).
Toxicity bioassays used surface water collected from Cell 11. Bioassays were conducted
using Ceriodaphnia. The bioassays were slightly toxic to test organisms. The percent of
sample resulting in a NOEC for reproduction, development, and survival was 50 percent
with a LOEC of 100 percent. The EC 50 was greater than 50 percent and the LC 50 was
70.7 percent.
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SECTION 4: RISK CHARACTERIZATION
Fish
Estimates of potential risk to fish (Table 4-4) indicated that dissolved copper and zinc pose a
probable risk (Category A) to fish. Both exceeded the CA-WQS acute value (for which, the
HQs were close to 1), however, zinc did not exceed the fish NOEC derived from toxicity
bioassays. This is most likely due to the fact that there was no toxicity observed in the
bioassay and the zinc concentration was low.
Toxicity bioassays used surface water collected from Cell 11. Bioassays were conducted
using topsmelt. Samples were not toxic to topsmelt at the highest concentration tested.
Accordingly, the NOEC was 100 percent of sample and the LOEC was greater than
100 percent.
4.2 Risk Description
The Risk Description evaluates the different sources of information concerning potential risks
including HQ risk estimates, results of toxicity bioassays, bioaccumulation testing, and any
observed ecological effects at the Lowlands to establish a weight-of-evidence for
determination of COECs. The weight-of-evidence for sediment/soil and surface water is
presented by area in the following subsections. The selected COECs are summarized for each
area in Table 4-5 (sediment/soil for terrestrial receptors), Table 4-6 (sediment/soil for aquatic
receptors and semi-aquatic birds), and Table 4-7 (surface water for aquatic receptors). Any
chemical with hazard quotient exceeding 1 was identified as a COEC. In addition, chemicals
showing significant bioaccumulation in Nereis were also retained as COECs.
4.2.1 Bolsa Bay
Potential risks were evaluated for aquatic and semi-aquatic receptors in Bolsa Bay. All
chemicals with HQs exceeding one were retained as COECs (Tables 4-6 and 4-7). A
summary of the potential for risk is presented below for each exposure medium.
4.2.1.1 Sediment/Soil
Review of the HQs for aquatic plants indicated that metals and selected PAHs
[benzo(a)pyrene and benzo(g,h,i)perylene] in sediments pose a possible risk (Category B)
COECs with the highest risk potential include arsenic and lead. Evaluation of exposures to
aquatic invertebrates exposed to Bolsa Bay sediment samples indicated that selenium,
nickel, and thallium had the highest potential for risks among the inorganics (Category A).
Among the organics, pesticides (4,4’-DDD, 4,4’-DDE, chlordane, and total DDT),
TPH-diesel, and waste oil were associated with the highest potential risks (Category A).
Evaluation of potential risks for semi-aquatic birds indicates that metals and pesticides pose
the highest risks (Category B – possible risk).
4.2.1.2 Surface Water
Chemicals exhibiting the highest HQs and exceeding RTVs for different receptor groups
consisted of metals, diesel, and waste oil. All chemicals with HQs greater than one were
similar in risk level. Copper was the only chemical exceeding acute criteria.
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SECTION 4: RISK CHARACTERIZATION
4.2.2 Full Tidal
Potential risks were evaluated for aquatic and semi-aquatic receptors in the Full Tidal area.
All chemicals with HQs exceeding one were retained as COECs (Tables 4-6 and 4-7). A
summary of the potential for risk is presented below for each exposure medium.
4.2.2.1 Sediment/Soil
Review of the HQs for aquatic plants indicated that metals and selected PAHs in sediments
pose a possible (i.e., both no effect and low effect levels were exceeded). COECs with the
highest risk potential include arsenic, barium, mercury, benzo(a)pyrene and
benzo(g,h,i)perylene.
For aquatic invertebrates, the highest probable risks (Category A) were observed for metals,
pesticides, and PAHs/diesel. The highest HQs were observed for dieldrin, chlordane
(technical, alpha, and gamma), 4,4’-DDD, 4,4’-DDE, and 4,4’-DDT.
Evaluation of potential risks for semi-aquatic birds indicates that metals – cobalt, copper,
zinc - and dieldrin pose possible risks.
4.2.2.2 Surface Water
Chemicals exhibiting the highest HQs and exceeding RTVs for different receptor groups
consisted of metals, pesticides, diesel, and waste oil. Chemicals with the highest HQs
consisted of diesel, chromium, and copper. Copper and endrin were the only chemicals
exceeding acute criteria.
4.2.3 Future Full Tidal
Potential risks were evaluated for terrestrial, aquatic, and semi-aquatic receptors in the
Future Full Tidal area. All chemicals with HQs exceeding one were retained as COECs
(Tables 4-5, 4-6, and 4-7). A summary of the potential for risk is presented below for each
exposure medium.
4.2.3.1 Sediment/Soil -Terrestrial Receptors
Chemicals with possible risks for terrestrial plants in the Future Full Tidal area are metals
and PAHs. Most exceedances had HQs greater than 10. Chemicals with the highest
exceedances consisted of arsenic, barium, chromium, cobalt, copper, lead, mercury, nickel,
selenium, thallium, vanadium, zinc, benzo(a)pyrene, and benzo(g,h,i)perylene.
Chemicals with the highest possible risks to terrestrial invertebrates included barium,
beryllium, chromium, mercury, and vanadium.
Chemicals posing possible risks to upland birds and mammals included several metals.
4.2.3.2 Sediment/Soil – Aquatic Receptors
Chemicals posing possible and probable risks to aquatic plants are those listed above for
terrestrial plants because the two receptor groups were evaluated using the same RTVs.
Estimated risks for aquatic receptors indicated that metals (cadmium, chromium, copper,
lead, mercury nickel, selenium, zinc), and pesticides (4,4,’-DDD, 4,4’-DDE, 4,4’-DDT,
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SECTION 4: RISK CHARACTERIZATION
chlordane – technical, alpha, and gamma, dieldrin) and PAHs (plus TPH diesel and waste
oil) have probable risk (Category A) and the highest HQs for exceedance of an acute RTV.
Chemicals posing a possible risk to semi-aquatic birds consisted of metals, pesticides, and
Aroclor 1254.
4.2.3.3 Surface Water
Chemicals posing probable risks (Category A) consisted of metals, pesticides, petroleum
products. Chemicals exceeding CA State water criterion for chronic effects consisted of
arsenic, copper, lead, nickel, 4,4’-DDT, and dieldrin. Copper (total and dissolved) also
exceeded acute toxicity values
4.2.4 Garden Grove-Wintersburg Flood Control Channel
Potential risks were evaluated for aquatic and semi-aquatic receptors in the Garden Grove
area. All chemicals with HQs exceeding one were retained as COECs (Tables 4-6 and 4-7).
A summary of the potential for risk is presented below for each exposure medium.
4.2.4.1 Sediment/Soil – Aquatic Receptors
Potential risks to aquatic plants resulted from to metals and PAHs. Chemicals with the
highest HQs consisted of arsenic, lead, benzo(a)pyrene, and benzo(g,h,i)perylene.
For sediment-related risks to aquatic invertebrates, probable risks (Category A) were
observed for selenium, 4,4’-DDD, 4,4’-DDE, chlordane (technical and alpha), phenanthrene,
and total DDT. Possible risks (Category B) were estimated for many metals, PAHs, and
dieldrin. Estimation of potential risks to semi-aquatic birds show that cobalt, copper, lead,
zinc, 4,4’-DDE, and Aroclor 1254 pose possible (Category B) risks.
4.2.4.2 Surface Water
Chemicals exhibiting the highest HQs and exceeding RTVs for different receptor groups
consisted of metals, pesticides, diesel, and waste oil. Chemicals with the highest HQs for
chronic effects consisted of cadmium, copper, nickel, vanadium, 4-nitorphenol, dieldrin, and
waste oil. Copper was the only chemical exceeding acute criteria.
4.2.5 Gas Plant Pond Area
Potential risks were evaluated for terrestrial, aquatic, and semi-aquatic receptors in the Gas
Plant Pond area. All chemicals with HQs exceeding one were retained as COECs (Tables 4-5,
4-6, and 4-7). A summary of the potential for risk is presented below for each exposure medium.
4.2.5.1 Sediment/Soil – Terrestrial Receptors
Potential risks to terrestrial plants resulted from metals and PAHs. Chemicals with the
highest HQs consisted of arsenic, copper, lead, thallium, benzo(a)pyrene, and
benzo(g,h,i)perylene.
Potential risks to terrestrial invertebrates resulted from 4 metals and one PAH. These were
arsenic, chromium, copper, vanadium, and acenaphthene. The hazard quotients were fairly
low, with the highest value being that for chromium.
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SECTION 4: RISK CHARACTERIZATION
Potential risks to upland birds and mammals were in the some possible range (Category C)
for metals. Arsenic in mice was the only chemical with a probable risk (Category B –
exceedance of a LOAEL).
4.2.5.2 Sediment/Soil – Aquatic Receptors
Potential risks to aquatic plants are the same as those reported for terrestrial plants in the
previous subsection because both receptors were evaluated using the same RTVs.
For sediment-related risks to aquatic invertebrates, probable risks were estimated for metals
(arsenic, chromium, selenium, thallium), pesticides (4,4’-DDD, total DDT), petroleumrelated
chemicals (acenaphthene, fluorene, napthalene, oil and grease, phenanthrene,
TPH-diesel, waste oil, low MW PAHs, total PAHs), total PCB, and di-n-octylphthalate.
Possible risks (Category B) were estimated for several other metals, pesticides, and PAHs.
Estimated risks to semi-aquatic birds were in the possible range for several metals (cobalt,
copper, lead, zinc), as well as 4,4’-DDE and Aroclor 1254.
4.2.5.3 Surface Water
Potential risks to aquatic organisms exposed to surface water were limited to diesel and
waste oil. Both had possible risks.
4.2.6 Muted Tidal Plus Rabbit Island
Potential risks were evaluated for terrestrial, aquatic, and semi-aquatic receptors in the
Muted Tidal and Rabbit Island area. All chemicals with HQs exceeding one were retained as
COECs (Tables 4-5, 4-6, and 4-7). A summary of the potential for risk is presented below for
each exposure medium.
4.2.6.1 Sediment/Soil – Terrestrial Receptors
Estimated risks to terrestrial plants were in the possible range (Category B) for metals and
PAHs. Chemicals with the highest estimated risk consisted of arsenic, barium, copper, lead,
benzo(a)pyrene, and benzo(g,h,i)perylene.
Chemicals that showed potential risks to terrestrial invertebrates were limited to metals,
most with lower HQs. The highest HQs were observed for barium and lead. Potential risks
to upland birds and mammals showed possible risks from lead. Some possible risks were
estimated for other metals. The highest HQs were observed for barium and lead.
4.2.6.2 Sediment/Soil – Aquatic Receptors
Potential risks to aquatic plants were the same as those listed above for terrestrial plants
because they were evaluated using the same RTVs.
For sediment-related risks to aquatic invertebrates, probable risks (Category A) were
estimated for metals (chromim, cobalt, copper, lead, nickel, selenium, thallium, and zinc),
pesticides (4,4’-DDD, 4,4’-DDE, 4,4’-DDT , chlordane [alpha, gamma, technical], dieldrin,
endrin, endrin aldehyde, endrin ketone, total DDT ), petroleum (acenaphthylene, fluorene ,
oil and grease, phenanthrene, TPH diesel, waste oil, low MW PAHs), and other organics
(di-n-ocylphthalate, total PCB). Possible risks (Category B) were estimated for several other
metals and PAHs. Potential risks to semi-aquatic birds were in the possible range for several
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SECTION 4: RISK CHARACTERIZATION
metals and pesticides including cobalt, copper, lead, zinc, 4,4’-DDE, and Aroclor 1254. The
highest HQs were observed for chromium, cobalt, lead, selenium, zinc, and 4,4’-DDD, and
4,4’-DDE. .
4.2.6.3 Surface Water
Potential risks to aquatic organisms exposed to surface water were limited to diesel and
waste oil. Both had possible risks.
4.2.7 Seasonal Ponds
Potential risks were evaluated for terrestrial, aquatic, and semi-aquatic receptors in the
Seasonal Ponds area. All chemicals with HQs exceeding one were retained as COECs
(Tables 4-5, 4-6, and 4-7). A summary of the potential for risk is presented below for each
exposure medium.
4.2.7.1 Sediment/Soil – Terrestrial Receptors
Estimated risks to terrestrial plants were in the possible range for metals and PAHs.
Chemicals with the highest estimated risk consisted of arsenic, barium, lead, and
benzo(a)pyrene.
Chemicals that showed potential risks to terrestrial invertebrates included metals and
PAHs; most with lower HQs. The highest HQs were observed for barium and chromium.
Potential risks to upland birds and mammals showed some possible risk (Category C) for
most of the exceedances. The highest HQs were observed for barium and chromium.
4.2.7.2 Sediment/Soil – Aquatic Receptors
Sediment-related risks to aquatic invertebrates were probable (Category A) for metals
(arsenic, chromium, lead, mercury, selenium, and thallium), pesticides (4,4’-DDD, 4,4’-DDE,
endrin, endrin aldehyde, and total DDT), petroleum (dibenzo[a,h]anthracene, oil and
grease, phenanthrene, TPH diesel, and waste oil), and other organics (di-n-octylphthalate).
Possible risks (Category B) were estimated for several additional metals and PAHs.
4.2.7.3 Surface Water
Chemicals exhibiting the highest HQs and exceeding RTVs for different receptor groups
consisted of metals, pesticides, diesel, and waste oil. Chemicals with the highest HQs for
chronic effects consisted of barium, silver sulfate, zinc, diazinon, TPH-diesel, and waste oil.
Copper and zinc were the only chemicals exceeding acute criteria.
4.3 Uncertainty Analysis
Uncertainties, which are inherent in all aspects of an ERA, include those related to Problem
Formulation, Analysis, and Risk characterization. The uncertainties and limitations associated
with this ERA Report, including the problem formulation, exposure characterization, and risk
characterization, are summarized in the following sections. Within this ERA, the uncertainties
are addressed qualitatively; no attempt was made to quantify the magnitude of specific
sources of uncertainty.
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SECTION 4: RISK CHARACTERIZATION
4.3.1 Problem Formulation
The Scoping Assessment (CH2M HILL, 1998b) was the basis for the problem formulation for
the EEC Report (CH2M HILL, 1999) and this ERA report, and uncertainties are primarily
associated with the limited availability of chemical stressor information at the time that the
document was produced. Other uncertainties are associated with the selection of
representative species and the identification of exposure pathways.
The stressor data available for the identification of COPECs was limited to hard-copy
reports from the Phase II sampling conducted by Tetra Tech (1996). The data were not
available in electronic format at that time, so evaluations were limited to screening the
maximum detected concentrations in each medium against screening-level benchmarks. In
addition, the nature and extent of contamination across the Lowlands could not be
evaluated because the Tetra Tech results were based on a focused sampling plan, whereby
only those locations with suspected toxicity were evaluated, and the ERA Sampling and
Analyses was just beginning. The electronic version of the Tetra Tech data was obtained, but
was found to be incomplete and not in a structure conducive to incorporation into the
database format necessary to calculate exposure point concentrations, estimate exposures, or
conduct Geographic Information System (GIS) mapping. This uncertainty was rectified in
this ERA with the acquisition and incorporation of the electronic database from the Tetra
Tech sampling (1996).
Representative species are selected to reduce uncertainty and to focus on species that are
both maximally exposed and representative of the wildlife using the site. However,
differences between species, including physiology, reproductive biology, or foraging habits,
can result in different exposures and sensitivities to different chemicals.
4.3.2 Analysis
The analysis consists of the exposure characterization and the ecological effects
characterization. Uncertainties related to these tasks are presented below.
4.3.2.1 Exposure Characterization
The uncertainties associated with the exposure characterization include limitations in the
background evaluation, assumptions made in calculating exposure point concentrations,
selection of exposure routes to quantify, and identification of species-specific exposure
parameters.
The evaluation of background inorganic levels in sediments included all samples collected
in the ERA Sampling and Analysis, including those samples collected from the dredge
footprint area. Some of these samples have been impacted by contaminants from onsite
activities or drainage to the Lowlands, which would have increased the levels of some of the
inorganic constituents. Dredge area sediment samples could not be readily separated by
depth because of different sampling approaches used there. For example, the surface
interval in the dredge area included at least the top 2 feet bgs, and may have included the
entire core (8 feet) if the core material was uniform rather than just the top 6 inches of
material (sampling was conducted to characterize each distinct layer of sediment that was at
least 2 feet thick). Therefore, the “surface sediment” data set includes samples that were
actually sampled to depths greater than 6 inches bgs. For this reason, a statistical analysis to
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SECTION 4: RISK CHARACTERIZATION
determine whether the mean surface and subsurface inorganic levels differed throughout
the Lowlands was not done. The estimate of background conditions was based on the “all
sample” data set.
Because there were no comparable offsite reference areas for Bolsa Chica, the estimate of
inorganic background levels was based on a qualitative evaluation of the cumulative percent
distribution curves for each constituent derived from onsite samples to indicate the
background or ambient levels. The determination of the curve break points required
professional judgment based on review of the data. Where the data sets contained a large
number of elevated non-detect (“U”-flagged) values, the curves were regenerated to
determine the distribution of detected values. This was done only for the “all sample” groups
of cadmium, mercury, selenium, silver, and thallium. There were a few elevated non-detect
values on some of the other “all sample,” surface, and subsurface cumulative percent plots.
However, the non-detects were not screened out of those data sets unless they directly
interfered with the interpretation of the break points for the cumulative percent curves.
The calculation of exposure point concentrations included assumptions that chemical
concentrations would remain constant over time, chemicals not detected or analyzed were
not present, and detected concentrations had the same bioavailability as those used in the
literature-reported toxicity tests or other toxicological studies. These assumptions may not
be realistic for all chemicals in all media, but they are generally conservative and represent
standard practice for conducting ERAs. The calculation of exposure point concentrations
was also limited by the lack of sample-specific reporting limits for non-detected chemicals in
the Tetra Tech data. Specifically, the electronic (and hardcopy version) of the Tetra Tech
data reported a “0” for non-detected chemicals rather than the detection limit. When
calculating summary statistics, non-detected chemicals are typically evaluated at one-half of
the reported detection limit. Because this information was not available, the non-detect
values were statistically evaluated at one-half of “0”, which equaled “0”. This results in a
downward or underestimation of the mean and 95th UCL. The 95th UCL was used to
estimate risks to mobile receptors (birds and mammals) and so these risks may be underestimated.
In addition, the summary statistical program used (SAS, 1990) did not
distinguish between detected chemicals and non-detected chemicals when selecting the
maximum value. If a ½ non-detect value was still greater than the maximum detected value,
the ½ non-detect value was selected as the maximum and used to estimate risks. This
resulted in an overestimation of many hazard quotients. Some were within the same order
of magnitude, but others were greater. The hazard quotients calculated using ½ non-detect
values are noted with an “*” in Tables 4-1 through 4-4.
Several exposure routes were considered minor and were not included in the exposure
analysis. Nonetheless, exposure via these other routes still contributes to the total risk to
each receptor; therefore, potential risks could have been underestimated because these
routes were not quantified. The routes of exposure that were not retained for quantitative
exposure evaluations include the following:
• Dermal contact with sediment/soil and surface water by birds or mammals
• Inhalation of volatiles from sediment/soil or surface water by birds or mammals
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Dermal contact with sediment or surface water is considered to be a minor secondary route
of exposure for birds and mammals. Dermal contact is of concern primarily with organic
chemicals that are lipophilic (i.e., have an affinity for fats) and can cross the epidermis of the
exposed organism. Although some COPECs are highly lipophilic (e.g., DDT) and can
bioaccumulate, they are of greater concern in the food chain pathway as opposed to direct
contact.
Inhalation of volatiles from sediment/soil or surface water is considered a minor exposure
route, primarily because of the low frequency of detection and the short half-life of most
volatile chemicals.
Exposure route assumptions were also made for each representative species, including rates
of ingestion and intake of exposure media (sediment/soil and biota). These factors, plus
other biological characteristics, influence potential exposure by a particular species and may
cause the selected species to be not truly representative of their guild. These differences may
not be accounted for by the representative species selected, which could result in an underor
overestimation of potential exposure (intake), depending on the species.
4.3.2.2 Ecological Effects Characterization
Uncertainties associated with the ecological effects characterization include salinity
adjustments required in the toxicity bioassays conducted on site sediment, pore water, and
surface water; the evaluation of those results through regression analyses; and the selection
of RTVs for use in the ERA.
The bioassays were conducted on standard toxicity testing organisms, but most of the
sediments and extracted pore waters had salinities outside of the tolerance ranges of the test
organisms. These sediments and pore waters had to be adjusted to salinities within the
tolerance range prior to bioassay test initiation so that false results would not be observed.
Salinity adjustments were required for more than one-half of the sediment samples used for
amphipod and Nereis tests and for more 80 percent of the pore waters used for Mytilus tests.
For pore waters, the dilution from salinity adjustment could be related to the actual test
dilutions used in the bioassays, but additional uncertainty arose in many samples because
the salinity dilutions resulted in no toxicity to test organisms when there were high
concentrations of chemicals in the undiluted sample. Adjusting the sample for salinity could
have also resulted in dilution of chemical concentrations or resulted in changes to
bioavailability or toxicity of some COPECs. The effects of dilution could not be quantitated
based on the methodologies used.
For the sediment bioassays, no correlation could be made because all sediments were tested
at 100 percent sample, and changes in salinity were made via the overlying waters. The
potential or actual changes in concentrations of other chemicals as a result of these
adjustments could not be quantified in any reliable way.
The evaluation of bioassay data through regression analyses provided an additional level of
data evaluation and additional effect concentrations. The uncertainties associated with the
regression analyses include data transformations, assumption that chemical concentrations
decreased linearly with dilution of the test medium for Mytilus bioassays, and the
estimation of EC 50 . The data were transformed to maximize the regression analyses so that a
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SECTION 4: RISK CHARACTERIZATION
dose-response effect could be observed if it were present. The data had to be transformed
back to the original state after the regression analyses so that the EC 50 could be estimated.
The transformation and then back-transformation can result in some uncertainty. The
uncertainty in the estimated EC 50 values is inversely proportional to both the sample size
and r 2 for the regression model on which they are based. As both sample size and
r 2 increase, confidence in the EC 50 increases. The best EC 50 measurements (e.g., those with
the least uncertainty) are based on models with the highest r 2 (i.e., > 0.5) and the largest
sample sizes, followed by EC 50 based on models with high r 2 and small sample sizes.
Moderate uncertainty is associated with EC 50 based on models where 0.2 < r 2 < 0.5. Given
the small amount of variation they describe, the EC 50 based on models with r 2 < 0.2,
regardless of sample size, are not recommended for use in remedial decisionmaking.
For Nereis (in sediment), topsmelt (in surface water), and Mysidopsis (in surface water), it
was not possible to determine the maximum concentrations of any chemicals that would not
cause significant effects (the NOECs) or the lowest concentrations that cause effects
(LOECs). This occurred because no effects were observed at the highest exposure
concentrations that were tested. Therefore, the NOECs and LOECs for those species
represent uncertainties, may result in an overestimation of the HQ.
Uncertainties associated with the selection of RTVs for use in the ERA include the effects
data available and extrapolations made. An attempt was made to identify RTVs for each
chemical for each receptor group, but toxicological information that can be correlated to
media concentrations is generally limited for terrestrial plants, invertebrates, and birds. In
general, RTVs for terrestrial receptors were limited to chronic no-effect and low-effect levels.
RTVs for aquatic receptors included both chronic and acute effect levels. As such, the
highest level of risk that could potentially quantified was Category B for terrestrial receptors
and Category A for aquatic receptors.
Lack of RTVs for several chemicals results in uncertainty of the risk posed by these
chemicals. Receptors that had the least number of RTVs available were terrestrial plants,
terrestrial invertebrates, and birds. RTVs were available for most chemicals for mammals
and aquatic receptors.
The other main source of uncertainty in RTVs is for those chemicals for which the only RTV
available was a NOEC based on a toxicity bioassay which did not show any toxicity. Since
there were no other RTVs with which to compare the HQs, it is unknown whether the HQ
represents an accurate estimation or is over-estimated. The other site-specific RTVs
(e.g., NOECs, LOECs, LC 20 s, and LC 50 s) were generally within the same magnitude as
established benchmarks, but not in all cases. Specifically, some LC 20 values were far more
conservative than ER-Ls.
4.3.3 Risk Characterization
Uncertainties related to the risk characterization include the use of hazard quotients to
quantify potential risks and the assumption that estimated risks for the representative
species will be protective of all similar receptors.
Hazard quotients are an estimate of potential risk and, while it can be conservatively
determined that if an HQ exceeds one there is a potential for risk, the magnitude of the HQ
cannot be used as a definitive measure of the risk. Different types of effect levels such as
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SECTION 4: RISK CHARACTERIZATION
no-effect levels, low-effect levels, and acute effect levels are used to aid in the weighting
of potential risks. In addition, results of toxicity bioassays are also used to increase the
confidence in the estimation of risk to a given receptor.
Given the differences in species, the estimated risks for one species may be over-or underrepresentative
of another species.
4.3.4 Overall Uncertainty
The uncertainties that have the greatest impact on the results of the ERA and their potential
impact are listed below:
• Use of ½ non-detect limits for estimating risk – overestimation of HQs. The HQs would
be lower if the actual value in that sample was much less than 1/2 the reporting limit
and the maximum detected value had been used. In some cases the HQ would have
been within the same order of magnitude, but in others, it would have been less and
may possibly have resulted in an HQ less than 1.
• Use of “0” for reporting non-detected chemicals – results in an underestimation of the
exposure point concentrations using the 95 th UCL. These calculations typically use ½ the
non-detect value. Use of “0”s lowers the 95 th UCL and as such lowers the resulting HQs.
• Lack of any RTV for a given chemical and receptor – level of impact varies based on
whether there is an RTV for the given chemical for another receptor group (e.g., RTVs
for 4,4’-DDD were not available for terrestrial plants or invertebrates, but were available
for birds and mammals). If the chemical can be evaluated at some trophic level, then
there is less uncertainty than if the chemical could not be evaluated at all.
• Lack of site-specific RTVs – level of impact varies depending on the chemical and
receptors potentially involved. Site-specific RTVs add power to the quantification of risk
and may provide RTVs where none were available in the literature, but if they
complement those available in the literature, then the impact is minimal.
Use of RTVs with inherent uncertainty – level of impact can be minimal or large. RTVs with
some uncertainty include those taken from older references (e.g., Long and Morgan, 1990) that
are not used in more recent references as well as those that are based on toxicity bioassays in
which there were no toxic effects. The use of older references had a minimal impact as they
allowed quantification of risks to some chemicals that would otherwise have no other
low-confidence RTVs. Use of NOECs from toxicity bioassays that had no toxic response
could have a larger impact and result in overestimated risks for those chemicals. This was
most apparent in the estimates for aquatic receptor exposure to sediment (Table 4-3).
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SECTION 5
Summary, Conclusions, and Recommendations
This section presents the summary, conclusions, and recommendations of the ERA for the
Bolsa Chica Lowlands. The objectives of the Bolsa Chica Lowlands project ERA consisted
of adequately characterizing of contamination in the Lowlands, providing
bioassay/bioaccumulation data necessary to assess ecological risks and to determine cleanup
criteria, to assess potential and actual risks to ecological receptors using the Lowlands,
and to aid in the design of wetland restoration. The ERA provides a format to achieve these
objectives and uses all of the available site information to evaluate potential effects to aquatic,
semi-aquatic, and terrestrial receptors under current and expected future conditions.
5.1 Summary
The ERA was conducted using a phased/tiered approach that was consistent with
established methodologies, but had been adapted to the specific needs of the Bolsa Chica
project. Phase I included an initial review of available data and resulted in the CSP/ERA
Work Plan (CH2M HILL, 1998a), and Scoping Assessment (CH2M HILL, 1998b). Phase II
consisted of the ERA Sampling and Analyses whereby additional site-specific data were
collected and evaluated resulting in the EEC Report (CH2M HILL, 1999 ) and Revised Work
Plan (CH2M HILL, 2000). Phase III consisted of the Focused Sampling and Analyses, during
which additional site-specific data were collected and evaluated to fill remaining data gaps,
and completion of this baseline ERA.
The analytical data used to characterize exposures consist of the sediment/soil, pore water,
surface water, and biota collected previously by Tetra Tech (1996) and by CH2M HILL/Kinnetic
Laboratories during the ERA Sampling and Analyses and the Focused Sampling and Analyses.
The results of data quality evaluation processes indicated that overall, the project data quality
objectives for precision, accuracy, representativeness, completeness, and comparability were
met (Appendix C) and the data set was of high quality.
The ERA Sampling and Analyses project component was designed to complete sampling for
areas away from known or suspected sources of contamination (random sampling
locations), to conduct toxicity bioassays and bioaccumulation studies using site-collected
sediment and water from both random and focused sampling areas, and to analyze fieldcollected
biota for chemicals that bioaccumulate. Random sampling was conducted in areas
away from known or suspected contamination, while focused sampling was conducted at
selected areas with known contamination.
The Focused Sampling and Analysis phase of the ERA occurred in 2000 to conduct more
detailed analyses of previously sampled “random” locations (sampled as part of the ERA
Sampling), and to identify the nature of contamination associated with previously identified
sources (such as sumps, wells, pipelines, maintenance areas, etc.) and potential sources. The
focused sampling locations were divided into three main categories: (1) Random Follow-up
sites, (2) Previously Uncharacterized sites (Cleanup Agreement and Release [CAR] sites),
and (3) Partially Characterized sites.
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CHAPTER 5: SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
This ERA Report was the culmination of the phased approach and incorporated/updated
information obtained in previous reports, evaluated results of all phases of field sampling as
well as data from the Tetra Tech Phase II Environmental Assessment (1996), and evaluated
potential risks to aquatic and terrestrial representative species identified for the Lowlands.
The major outputs from the ERA consisted of the development of the ecological conceptual
site model (Problem Formulation), the exposure profile (Exposure Characterization), the
stressor-response profile (Ecological Effects Characterization), and the risk description (Risk
Characterization).
Problem Formulation
The major product of the Problem Formulation was the ecological conceptual site model.
This model combined information on COPECs, potential ecological receptors, potential
exposure pathways, assessment endpoints and measures to provide an overall picture of
potential for exposure and risk at the site. This model (shown graphically in Figure 2-5) was
then used to focus the remainder of the ERA.
Exposure Characterization
The potential exposure of receptors to COPECs in the Lowlands was determined via the
Exposure Characterization. The primary product of the Exposure Characterization was the
exposure profile. The exposure profile established a relationship between stressors and
potential receptors through: (1) identification of potential sources of chemical stressors (the
COPECs) and their spatial distribution across the site, (2) calculation of exposure point
concentrations for various exposure media and receptors based on the most likely exposure
scenario for each species, and (3) calculation of reasonable maximum daily dosages for
chemical intake from abiotic and biotic sources by terrestrial and semi-aquatic birds and
terrestrial mammals
The Lowlands were divided into areas with similar habitat types under current and/or
post-restoration conditions for purposes of evaluating potential risk. The specific Cells
included in each area are:
• Bolsa Bay – Inner Bolsa Bay (Cell IB) and Outer Bolsa Bay (Cell OB)
• Full Tidal – Cells 1, 1A, 3 through 8, 15 through 18, 43, 44, 51, 58, 59, 61, and 62
• Future Full Tidal – Cells 14, 19 through 40, and 63
• Garden Grove – Wintersburg Flood Control Channel – Cell 52
• Gas Plant Pond Area – offsite areas downgradient from the former Gas Plant, south of
Cells 11 and 12
• Muted Tidal plus Rabbit Island – Cells 41, 42, 45 through 50, 53, 55, 60, 66, and 67
• Seasonal Ponds – Cells 2, 9 through 13
• Sitewide (biota only) – terrestrial invertebrates that were composited from throughout
the Lowlands
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CHAPTER 5: SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
The evaluation of background levels for inorganic constituents in sediments was completed
using samples collected from onsite focused and random sample locations (including those
within the proposed dredge area footprint). Maximum concentrations of chemicals
considered to be background levels in surface and subsurface sediments and a combined
value for all sediments were estimated; this was accomplished using cumulative
distribution plots in which detected and non-detected results were evaluated together and
separately to distinguish the impact of non-detected results on the distribution and
estimated background concentrations. Maximum background values for the combined data
set were estimated for arsenic (11 mg/Kg), barium (110 mg/Kg), beryllium (0.94 mg/Kg),
cadmium (0.66 mg/Kg), chromium (43 mg/Kg), cobalt (10.1 mg/Kg), copper (26.1 mg/Kg),
lead (48 mg/Kg), mercury (0.28 mg/Kg), nickel (30 mg/Kg), selenium (0.54 mg/Kg), silver
(0.22 mg/Kg), thallium (0.61 mg/Kg), vanadium (75 mg/Kg), and zinc (103 mg/Kg). These
site specific background levels were higher (2 to 6 times) than the preliminary background
used in the Scoping Assessment (Table 2-12).
The exposure profile outlined the receptors and exposure routes that were most likely to
occur at the Lowlands, and the basis for the exposure point concentration as listed below:
• Terrestrial plants - Direct contact via root uptake from sediment/soil. Exposure point
concentrations based on the maximum reported value for each chemical detected.
• Terrestrial invertebrates - Direct contact with and ingestion of sediment/soil. Exposure
point concentrations based on the maximum reported value for each chemical detected.
• Belding's savannah sparrow - Ingestion of terrestrial plants, terrestrial invertebrates,
sediment/soil, and surface water. Exposure point concentrations based on the 95 th UCL
value for each chemical detected.
• American kestrel - Ingestion of terrestrial invertebrates, small mammals, sediment/soil,
and surface water. Exposure point concentrations based on the 95 th UCL value for each
chemical detected.
• Black-crowned night-heron - Ingestion of aquatic invertebrates, fish, small mammals,
sediment/soil, and surface water. Exposure point concentrations based on the 95 th UCL
value for each chemical detected.
• Black-necked stilt - Ingestion of aquatic invertebrates, sediment/soil, and surface water.
Exposure point concentrations based on the 95 th UCL value for each chemical detected.
• Least tern - Ingestion of fish, sediment/soil, and surface water. Exposure point
concentrations based on the 95 th UCL value for each chemical detected.
• Western harvest mouse - Ingestion of terrestrial plants, invertebrates, sediment/soil, and
surface water. Exposure point concentrations based on the 95 th UCL value for each
chemical detected.
• Coyote - Ingestion of terrestrial plants, bird eggs, small mammals, sediment/soil, and
surface water. Exposure point concentrations based on the 95 th UCL value for each
chemical detected.
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CHAPTER 5: SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
• Aquatic plants – Direct contact/root uptake from sediment/soil and surface water.
Exposure point concentration based on the maximum reported value for each chemical
detected.
• Aquatic macroinvertebrates - Direct contact with and ingestion of sediment/soil.
Exposure point concentration based on the maximum reported value for each chemical
detected.
• Fish - Direct contact with surface water. Exposure point concentration based on the
maximum reported value for each chemical detected.
Ecological Effects Characterization
The Ecological Effects Characterization focused on (1) evaluating site-specific effects data to
determine the potential adverse effects that may result from different concentrations of
chemical stressors, and (2) establishing a link between these effects and the assessment
endpoints and ecological conceptual site model. The product of this portion of the ERA was
the stressor-response profile that was combined with the exposure profile to conduct the
Risk Characterization. The stressor-response profile summarized the potential effect levels
for different receptors that are related to the assessment endpoints for the ERA. These effect
levels included:
• NOECs, NOAELs, LOECs, LOAELs and other toxicity-based endpoints – Obtained from
the literature for terrestrial receptors (plants, invertebrates, birds, and mammals) (see
Tables 3-25 through 3-28)
• LC 20 s and LC 50 s for survival of aquatic invertebrates in sediment – Derived from the
regression analyses conducted on amphipod toxicity bioassay results. (See Table 3-29)
• NOECs for survival of aquatic invertebrates in sediment – Calculated from polychaete
worm toxicity bioassay results (see Table 3-29)
• EC 20 s and EC 50
s for larval development of aquatic invertebrates in pore water – Derived
from the regression analyses conducted on bivalve toxicity bioassay results (see
Table 3-30)
• NOECs for survival and growth of fish in surface water – Calculated from fish toxicity
bioassay results (see Table 3-30)
• NOECs and/or LOECs for survival, growth, reproduction, and/or fecundity for aquatic
invertebrates - Calculated from Ceriodaphnia and Mysidopsis toxicity bioassay results (see
Table 3-30).
Risk Characterization
The Risk Characterization presents the evidence linking COPECs to potential adverse effects
in the Lowlands including calculation of HQs and evaluation of site-specific toxicity bioassays
and bioaccumulation studies to provide a weight-of-evidence for potential risks and identify
COECs. The identification of COECs was presented in Figure 4-1. All COPECs that exceeded
any available RTV as well as chemicals that showed significant bioaccumulation in Nereis
clam worms were retained as COECs. The overall risk posed by a COEC in a given medium
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CHAPTER 5: SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
and evaluation area was determined based on the types of RTVs that were exceeded (i.e., noeffect
levels vs. low-effect levels and chronic effect levels vs. acute effect levels). The overall
risk categories were defined as follows:
• Unknown – RTVs were not available, so risk could not be quantified.
• None – Exposure does not exceed any of the available RTVs.
• Uncertain – Exposure exceeds a no-effect level, but risk could not be fully quantified
because a low-effect level was not available (Category U).
• Some Possible Risk – Exposure exceeds a no-effect level, but not a chronic low-effect
level (Category C).
• Possible Risk – Exposure exceeds a chronic low-effect level, but not an acute effect level
(Category B).
• Probable Risk – Exposure represents the highest level that could be quantified. Exposure
exceeds an acute effect level or showed significant bioaccumulation in Nereis clam
worms (Category A).
The COECs in each medium for terrestrial and aquatic receptors were presented in Tables 4-5
through 4-7.
Terrestrial Receptors
The primary chemicals in sediment/soil showing potential for risk to terrestrial receptors
consisted of metals and some PAHs (Table 4-5). The highest level of risk that could be
quantified for terrestrial receptors was Category B (possible risk) because RTVs were limited
to chronic no-effect and low-effect levels; acute RTVs were not identified. Therefore, it is
possible that the risk is underestimated for terrestrial receptors at the Bolsa Chica site. These
risks are located throughout the terrestrial portions of the existing and future restored site
including parts of the Future Full Tidal, Gas Plant Pond, Muted Tidal, and Seasonal Pond
areas.
Aquatic Receptors and Sediment Exposure
The chemicals in sediment/soil that showed the highest potential for risk (Category A) to
aquatic receptors included metals, pesticides, some PAHs, and TPH-diesel and waste oil
(Table 4-6). In addition, significant bioaccumulation of metals and pesticides in Nereis clamworms
was observed for several evaluation areas. All COECs that also had significant
bioaccumulation were considered to pose a probable risk (Category A) based on
comparisons to RTVs, with the exception of lead and vanadium in the Full Tidal area. These
chemicals were estimated to pose a possible risk (Category B) to aquatic receptors.
The Future Full Tidal area had both the greatest number of COECs present and the highest
magnitude of risk overall due to sediment /soil contamination, whereas Bolsa Bay and the
Garden Grove channel had fewer COECs and a lower magnitude of risk from sediment/soil
contamination.
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CHAPTER 5: SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
Aquatic Receptors and Water Exposure
The chemicals in surface water that showed probable risk (Category A) to aquatic receptors
were limited to copper, zinc, and endrin as these chemicals were the only ones that
exceeded the CA-WQS acute level (Table 4-7). Possible risk (Category B) was estimated for
several other metals, pesticides, and TPH-diesel and waste oil.
The Future Full Tidal area had both the greatest number of COECs present and the highest
magnitude of risk overall due to surface water quality, whereas the Gas Plant Pond and
Muted Tidal areas had few COECS present and none that exceeded acute level RTVs.
Overall
Metals, some PAHs and petroleum products (TPH-diesel and waste oil) were found to
consistently exceed toxic levels in many areas of the site for many receptors (terrestrial and
aquatic). These chemicals are consistent with those that are associated with the oil and gas
exploration, production and processing activities that have occurred on the site for many
decades. Pesticides were also found to be widespread throughout the site. On-site pesticide
application is known to have occurred for mosquito control in previous decades.
Additionally, urban and agricultural run-off from surrounding areas has likely contributed
to certain metal and pesticide concentrations found on-site.
5.2 Conclusion
Because this ERA identified a link between exposure to chemical concentrations on this site
and adverse effects to plants or wildlife that occur there, it has established that on-site
availability of contaminated sediment/soil or water presents a risk of adverse effects to
important ecological resources.
Many chemicals were identified that pose risk to terrestrial and aquatic receptors. Most
notably, metals, pesticides, PAHs, and TPH-diesel and waste oil consistently show possible
(Category B) and probable (Category A) risks to receptors.
Based on the results concerning the geographic extent of the contamination, the number of
individual COECs and the pathways of exposure, the risk to plants and wildlife on the Bolsa
Chica site from sediment/soil contamination is likely greater than from surface water
contamination. Similarly, the risk of adverse effects to aquatic and semi-aquatic receptors is
likely greater than the risk to terrestrial receptors.
Without remediation, the impacts to plants and wildlife in certain areas of the Bolsa Chica
site will remain high including continuing contaminated habitat for certain benthic species
at chemical concentrations causing chronic or acute impacts, continuing chemical
contamination in the food chain resulting in chronic or acute impacts to wildlife feeding on
the site and bioaccumulation of certain chemicals into higher trophic levels possibly causing
reduced productivity.
The results of the ERA provide the basis for determining appropriate clean-up goals for the
Bolsa Chica site. The level of risk to terrestrial and aquatic receptors can be reduced from
current conditions (presence of known concentrations exceeding acute [or chronic] effects
levels) to a future restored state that would reduce the risk by reducing exposure
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CHAPTER 5: SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
concentrations to those below acute or chronic effects levels. This reduction in risk will
contribute to achievement of the management goals for the site, which are stated as follows:
• Sediment, surface water quality, and food source conditions capable of supporting
terrestrial, aquatic, and semi-aquatic plant and wildlife populations that would typically
be found in Full Tidal and Managed Tidal coastal wetland habitats, and non-tidal
Seasonal Ponds.
• Sediment, surface water quality, and food source conditions supportive of individuals of
special-status biota and migratory birds protected under the Migratory Bird Treaty Act
likely to be found in Full Tidal and Managed Tidal coastal wetland habitats, and nontidal
Seasonal Ponds.
5.3 Recommendations
Chemicals that were not identified as COECs fall into two categories: (a) those that have low
or no potential for exposure or risk and (b) those that have no known reference toxicity
values for the receptors we evaluated. The development of clean-up strategies for these
chemicals is not recommended.
Chemicals identified as COECs in the Bolsa Chica Lowlands are recommended for further
evaluation or remediation. Clean-up goals should be developed based on the receptors that
may be at risk.
The integrated nature of the exposure (through surface water, sediment/soil and food web
pathways) demonstrates a need to remove the contamination at the source. In most
instances, clean-up of COECs in the sediment/soil would provide the greatest opportunity
to reduce the risk through improving the habitat and reducing the exposure potential to
lower trophic organisms and thus reducing the contamination throughout the food chain.
The following factors should be considered in the development of clean-up goals:
• Magnitude of observed concentrations and toxic concentrations as defined by the
reference toxicity values in this ERA
• Likelihood of persistence of contamination without remediation
• Functional value and uniqueness of the Bolsa Chica site in relation to the surrounding
area
• Recovery potential of the site
• Short-term and long-term impacts of clean-up on the site habitat and larger ecosystem
• Effectiveness of a clean-up effort; that is, whether there are other continuing, nearby
contaminant releases that will continue to adversely affect the ecosystem after cleanup is
implemented
The results of the ERA provide adequate information to evaluate the need for clean-up and
appropriate levels of clean-up. However, additional delineation of individual sites is needed
to determine the bounds of the clean-up effort.
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SECTION 6
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SECTION 6: REFERENCES
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ERA REPORT 6-8 SAC/143368(006.DOC)
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SECTION 6: REFERENCES
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