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M m <br /> D Table 2-2 <br /> Summary of Impacts and Mitigation Measures <br /> C„ Significance Significance <br /> 3 Impacts Before Mitigation Measures After <br /> Mitigation Mitigation <br /> project.Based on these findings,the proposed project would <br /> have a less-than-significant impact on the upstream spawning <br /> migrations of adult fishes. <br /> 4.13-2: Thermal Effects on Fish and Benthic PS 4.13-2: Thermal Effects on Fish and Benthic Macroinvertebrates LTS <br /> Macroinvertebrates Exposed to the Plume While Moving Exposed to the Plume While Moving Downstream Past the <br /> Downstream Past the Discharge Outfall.At full build-out,the Discharge Outfall.The City of Manteca will design,install,and <br /> proposed project would result in a thermal plume of increased operate a treated effluent cooling tower or an equivalent technology <br /> temperatures,relative to the ambient temperatures,across that cools treated effluent prior to discharge into the San Joaquin <br /> portions of the water column,under all conditions,that is larger River.The cooling tower or equivalent technology will be designed <br /> than the thermal plume that currently exists(and permitted) to reduce the temperature of the treated effluent by up to 15°F such <br /> downstream of the discharge outfall.The project-specific that the effluent discharge and associated size and intensity of the <br /> changes to the size and characteristics of this plume would be thermal plume will not result in adverse thermal affects to the health <br /> considerable,as would project-specific effects on the frequency and/or condition of sensitive fish species and will comply with all <br /> with which specific plume characteristics occur.A zone of California Thermal Plan Objectives,which have been established to <br /> passage would remain along the west bank river margin of the be protective of beneficial uses. The reduction in temperature of the <br /> water column where river temperatures are unaffected by treated effluent will prevent the creation of a lethal zone or plume, <br /> discharges.When achievable,actively swimming young-of-the- defined as water temperatures that are at or above the lethal effects <br /> year fishes emigrating from upstream rearing areas would select levels(i.e.,>68°F)during time periods when the most sensitive fish <br /> migration routes past the discharge outfall that avoid elevated species would be in the vicinity of the WQCF outfall(i.e.,from <br /> temperatures and excessive temperature differentials.The January to May)and ambient background temperatures are at or <br /> macroinvertebrate communities inhabiting the sediments and below these lethal effects levels.Because the ambient water <br /> CD <br /> v drifting through the plume are generally tolerant of the absolute temperature of the San Joaquin River can exceed the>68°F lethal <br /> ptemperature regime and differences created by the proposed effects threshold during the later portion of the time period when <br /> T project,particularly for the relatively short period of time they sensitive species are present(e.g.,April and May),the temperature of <br /> M would be drifting through the plume.However,passively the treated effluent produced by the cooling tower or equivalent <br /> 0- drifting fish are typically transported past the discharge in the technology may be greater than ambient background river <br /> o near-shore habitats and along the upper portion of the water temperatures under these conditions and during these periods.This <br /> CD <br /> column,both of which are noticeably affected by the effluent could result in conditions where the plume exceeds the lethal effects <br /> plume.Based on the findings for passively drifting fish being threshold;however,with implementation of the cooling tower or <br /> noticeably affected by the thermal plume,the proposed project equivalent technology,the size and intensity of the plume will be <br /> m would have a potentially significant impact on the populations minimized resulting in only short-term exposure(through reduced <br /> and communities of fish moving downstream in the lower San plume size)to marginally increased water temperatures. Because <br /> 0 v Joaquin River and Delta. sensitive fish species have been documented(Moyle 2002, <br /> oBartholow and Henricksen 2004,Bjorn and Reiser 199 1)to survive <br /> v exposure to higher temperatures(beyond lethal effects thresholds)for <br /> Cn short periods of time, substantial adverse impacts to fish would not <br /> voccur. <br /> LTS=Less than Significant S=Significant PS=Potentially Significant SU=Significant and Unavoidable <br />