1.1 MB pdf - Bolsa Chica Lowlands Restoration Project

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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 SAC/143368(002.DOC) 2-13 ERA REPORT 7/31/02
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. ERA REPORT 2-14 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 RareFind. 199
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SECTION 6: REFERENCES Wentsel, R. S
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