1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

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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.<strong>1.1</strong> 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). SAC/143368(003.DOC) 3-25 ERA REPORT 7/31/02
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. ERA REPORT 3-26 SAC/143368(003.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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SECTION 6: REFERENCES Dunteman, G.
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SECTION 6: REFERENCES Kauss, P. B.
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SECTION 6: REFERENCES RareFind. 199
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SECTION 6: REFERENCES U.S. EPA. 199
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SECTION 6: REFERENCES Wentsel, R. S
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