1.1 MB pdf - Bolsa Chica Lowlands Restoration Project
1.1 MB pdf - Bolsa Chica Lowlands Restoration Project 1.1 MB pdf - Bolsa Chica Lowlands Restoration Project
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.) SAC/143368(001.DOC) 1-7 ERA REPORT 7/31/02
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 ERA REPORT 1-8 SAC/143368(001.DOC) 7/31/02
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SECTION 1: INTRODUCTION<br />
• Chemicals not detected in some samples were assumed present in those samples at half<br />
their sample-specific reporting limit, if they were detected at least once within a defined<br />
evaluation area.<br />
• Chemicals not detected in any sample collected for a given medium (e.g., sediment)<br />
were assumed not present.<br />
• The exposure point concentration was considered the concentration of each chemical in<br />
a specific exposure medium that represents the maximum reasonable exposure for each<br />
biological receptor. This value was used to estimate potential risks to a specific receptor<br />
through comparison to effect levels developed from site-specific bioassays and literature<br />
information.<br />
• The exposure point concentrations for immobile or relatively sedentary receptors (aquatic<br />
and terrestrial plants and invertebrates) were the observed maximum concentrations for<br />
chemicals detected in each evaluation area.<br />
• The exposure point concentrations for receptors with limited movement in the <strong>Lowlands</strong><br />
(fish) were the observed maximum concentrations detected in each evaluation area. This<br />
selection was based on the physical limitations to their mobility (because they are unable<br />
to move between cells) and the limited availability of surface water data. (For most<br />
analytes, sufficient data were not available to calculate a 95-percent upper confidence<br />
level [UCL] of the mean.)<br />
• The exposure point concentrations for mobile receptors (birds and mammals) were the<br />
95-percent UCL of the mean for chemicals detected in the exposure area, unless the 95-<br />
percent UCL exceeded the maximum detected concentration, in which case the<br />
maximum detected concentration was the exposure point concentration.<br />
• The exposure point concentration for each chemical is as bioavailable as the chemical on<br />
which the toxicity information is based.<br />
• The toxicological information used represents site-specific bioassay results in<br />
combination with information available from literature and database searches.<br />
• The primary exposure pathways for aquatic organisms are ingestion and direct contact<br />
with sediment and surface water.<br />
• The primary exposure pathways for semi-aquatic and terrestrial organisms are direct<br />
contact with soil (plants); direct contact and ingestion of soil (invertebrates); and<br />
ingestion of sediment/soil, surface water, and food (birds and mammals). (Direct<br />
contact and inhalation exposures were not quantitatively evaluated for birds and<br />
mammals. The contribution of these pathways to the overall risk is expected to be minor<br />
in comparison to other pathways evaluated, and available dermal and inhalation<br />
toxicological information is limited.)<br />
SAC/143368(001.DOC) 1-7 ERA REPORT<br />
7/31/02
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