1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

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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. SAC/143368(002.DOC) 2-11 ERA REPORT 7/31/02
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. ERA REPORT 2-12 SAC/143368(002.DOC) 7/31/02
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CHAPTER 5: SUMMARY, CONCLUSIONS, AN
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SECTION 6 References Abbasi, S. A.
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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 Wentsel, R. S
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