1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

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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. SAC/143368(004.DOC) 4-23 ERA REPORT 7/31/02
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 <strong>Lowlands</strong> 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 <strong>Lowlands</strong>, 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 ERA REPORT 4-24 SAC/143368(004.DOC) 7/31/02
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REVISED FINAL VOLUME I Ecological R
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CONTENTS 3. Analysis...............
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CONTENTS 3-21 Summary of EC 50 s an
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Executive Summary The Bolsa Chica L
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EXECUTIVE SUMMARY The ERA report ev
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EXECUTIVE SUMMARY “focused sampli
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EXECUTIVE SUMMARY Exposure point co
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EXECUTIVE SUMMARY sample. However,
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EXECUTIVE SUMMARY The chemicals in
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SECTION 1: INTRODUCTION • Sedimen
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SECTION 1: INTRODUCTION Assessment
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SECTION 1: INTRODUCTION Based on th
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SECTION 1: INTRODUCTION 1.5 Organiz
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SECTION 2:PROBLEM FORMULATION The L
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SECTION 2:PROBLEM FORMULATION The e
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SECTION 2:PROBLEM FORMULATION 2.2.1
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SECTION 2:PROBLEM FORMULATION tern
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SECTION 2:PROBLEM FORMULATION backg
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SECTION 2:PROBLEM FORMULATION 2.4.1
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SECTION 2:PROBLEM FORMULATION The f
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SECTION 2:PROBLEM FORMULATION Benth
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SECTION 2:PROBLEM FORMULATION Fish
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SECTION 3: ANALYSIS The field sampl
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SECTION 3: ANALYSIS CAR Sites A tot
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SECTION 3: ANALYSIS 3.1.2 Data Eval
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SECTION 3: ANALYSIS questionable. T
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Page 117 and 118: SECTION 6 References Abbasi, S. A.
Page 119 and 120: SECTION 6: REFERENCES Dunteman, G.
Page 121 and 122: SECTION 6: REFERENCES Kauss, P. B.
Page 123 and 124: SECTION 6: REFERENCES RareFind. 199
Page 125 and 126: SECTION 6: REFERENCES U.S. EPA. 199
Page 127: SECTION 6: REFERENCES Wentsel, R. S
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