ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

Home Browse Search

In addition to changing the existing thermal plume that occurs immediately downstream of the discharge outfall, discharges under the proposed condition full-build-out condition constitute a point-source heat load to the system. This assessment evaluates the incremental increase in the fully mixed San Joaquin River/Delta water temperatures that could occur under the proposed project full build-out condition,relative to the existing permitted condition. Model simulations for nominal San Joaquin River flow rates of 600 cfs and 1,250 cfs were performed to evaluate the proposed project's incremental effects on downstream Delta locations under critical and dry/below normal water years,respectively. The minimum and maximum calculated WQCF effluent contributions for selected locations within the Delta are listed in Appendix C (Tables 35 and 36) corresponding to critical and dry/below normal water years,respectively. In general,the farther away from the WQCF discharge the far-field site is located,the lower the percent contribution of WQCF effluent, and as WQCF discharge increases, so does its percent contribution at far-field locations. The calculated WQCF percent contribution exceedance plots are presented for selected Delta locations in Appendix C(Figures 27 through 32). For example, from Figure 27, less than 0.5%of the water at the SWT Clifton Court intake will be of WQCF origin for 70% of a critical water year; and for 85%of a dry/below normal water year at a WQCF full build-out discharge rate of 27 mgd. Lower WQCF discharge results in lower percent contributions of WQCF effluent at far-field locations. Because the proposed project(at full build-out)would result in a fully mixed regime downstream of the discharge that is near equivalent to that under the existing permitted condition(<1%effluent contribution)under all conditions above critical water year flows rates,these effluent contributions would result in negligible incremental increases in downstream water temperatures. Therefore,this impact is less than significant. Other Water Quality Parameters and Priority Pollutants The assessments of all other water quality related effects of the proposed project on aquatic life(i.e., fisheries and aquatic resources)within the affected project area are contained within the various numbered,constituent-specific impact assessments of Section 4.9 (Hydrology and Water Quality). Temporary Construction-related Effects on Water Quality The assessment of temporary construction-related effects on San Joaquin River water quality and its fisheries and aquatic resources is contained in Section 4.9 (Hydrology and Water Quality). 4.13.3 MITIGATION MEASURES No mitigation is necessary for the following less-than-significant impacts: 4.13-1: Potential for Thermal Plume below the Discharge Outfall to Block or Substantially Delay the Upstream Spawning Migrations of Fishes 4.13-3: Population-or Community-Level Effects to Fish or Macroinvertebrates from the Incremental Increase in Downstream Water Temperatures (Fully Mixed Condition) The following mitigation measure is provided for the potentially significant impact: Mitigation Measure 4.13-2: Thermal Effects on Fish and Benthic Macroinvertebrates Exposed to the Plume While Moving Downstream Past the Discharge Outfall.The City of Manteca will design, install, and operate a treated effluent cooling tower or an equivalent technology that cools treated effluent prior to discharge into the San Joaquin River. The cooling tower or equivalent technology will be designed to reduce the temperature of the treated effluent by up to 15°F such that the effluent discharge and associated size and intensity of the thermal plume will not result in adverse thermal affects to the health and/or condition of sensitive fish species and will EDAW Manteca WQCF and Collection System Master Plans EIR Fisheries and Aquatic Resources 4.13-26 City of Manteca