ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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objectives(State Water Quality Control Plans), and NPDES limitations. If consistent compliance with the applicable water quality criteria/objectives and NPDES permit limitations was demonstrated for the proposed project condition, and the applicable regulatory criteria/objective and permit limitations were considered protective of aquatic life resources,then it was determined that the parameter concentration/level in the receiving water would not adversely affect fisheries and aquatic resources. This evaluation was conducted for both near- field and far-field locations,downstream of the discharge outfall as well as for constituents assessed that were not modeled. If consistent compliance under the proposed project condition is anticipated,but current scientific information pertaining to the parameter indicated that the current criteria/objective(s)and/or NPDES limitation(s)is/are not adequately protective of aquatic life,or if no criteria,objective,or NPDES limitation currently exists for the parameter(e.g.,nutrients),then a scientific assessment,using the current and available scientific literature,was performed. This assessment addressed the potential for the parameter to affect aquatic resources downstream of the discharge, at the concentrations/levels documented for the proposed project condition. If initial evaluations indicate that consistent compliance with applicable criteria,objective(s), and/or NPDES limitation(s) could not be achieved under the proposed project condition, a scientific evaluation,using the available scientific literature, also was performed. This evaluation was conducted to determine whether the anticipated magnitude and frequency of criteria/objective or permit limitation exceedance would be expected to result in adverse impacts to fish or other aquatic resources downstream of the discharge outfall. For example, at the onset of preparing this chapter, it was known that: 1. the current Manteca WQCF discharge cannot consistently comply with the Thermal Plan temperature objectives applicable to this facility, and thus exceptions to the Thermal Plan are being sought(to be incorporated into the current NPDES permit's temperature limitations); and 2. the Thermal Plan objectives are not necessarily based on the current science regarding thermal effects of the Manteca WQCF discharge on anadromous salmonids and other aquatic biota using the lower San Joaquin River. Consequently, a thorough technical assessment,using the available scientific literature,was performed to determine the potential for project-specific thermal impacts to aquatic resources. Temperature Aquatic life uses are the only beneficial uses of the lower San Joaquin River and Delta that could be affected by the thermal effects of the proposed project. The applicable Thermal Plan objectives and current NPDES permit limitations are not well supported by current scientific information pertaining to thermal effects on aquatic life. Therefore, compliance with these thermal limits does not necessarily provide an adequate means by which to assess actual thermal impacts to aquatic life in the San Joaquin River and Delta. Rather,a scientific assessment of thermal effects on fish and macroinvertebrates was performed. As discussed above (see section 4.13.1,"Environmental Setting"), a variety of fish and macroinvertebrates inhabit the lower San Joaquin River. These include Chinook salmon, steelhead, striped bass, and a number of other native and nonnative resident and migratory species. The potential biological effects of exposure of fish and other aquatic organisms to elevated water temperatures are a function of a variety of factors including the duration of exposure,the magnitude of temperature exposure, acclimation temperature,life stage, and species. The response and tolerance of aquatic organisms to elevated water temperatures varies substantially among species. Responses to temperature exposure may include,but are not limited to, acute mortality, sub-lethal physiological changes, behavioral avoidance,behavioral attraction, and changes in feeding and growth rates. Assessing the potential effects of the Manteca WQCF discharge on aquatic organisms inhabiting the lower San Joaquin River in the vicinity of the existing discharge includes consideration of the seasonal timing for when organisms would be present in the area and potentially exposed to the discharge, ambient(acclimation)water temperatures, and the EDAW Manteca WQCF and Collection System Master Plans EIR Fisheries and Aquatic Resources 4.13-16 City of Manteca