ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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smolt life stages of anadromous salmonids are believed to use the upper one-third of the water column and the river margins,with the larger smolts more likely to use the center of the channel(Dauble et al. 1989). The lower San Joaquin River near the Manteca WQCF discharge outfall is channelized;has extensive riprap along the banks; is characterized by a lack of near-shore woody debris or other structures, shading, and backwater areas;has relatively swift,tidally influenced currents; and has relatively high water temperatures during the late spring, summer, and fall months. As such,the river in this location does not provide the kind of habitat elements that would encourage salmonid rearing;rather, it serves as a migration corridor to better rearing habitats at downstream Delta locations (Yoshiyama et al. 1996). Consequently,movement of actively swimming anadromous salmonid emigrants past the WQCF outfall area is believed to occur rather rapidly,with juvenile salmonids rearing in the more complex slough habitats of the central and west Delta prior to ocean entry. Regarding thermal tolerances and preferences of Chinook salmon, Brett(1952)reported that juvenile Chinook salmon acclimated to a temperature of 59°F and had an upper lethal temperature of>77°F (for a one-week exposure). Bjornn and Reiser(1991) state that the upper lethal limit for steelhead is approximately 75°F and that salmonids usually try to avoid stressful temperature conditions when possible by moving to other areas. Gray et al. (1977)reported that juvenile Chinook salmon avoided heated thermal plumes when plume temperatures were 16°F to 19°F above ambient water temperature. These authors report that behavioral adaptations may prevent juvenile Chinook salmon in nature from experiencing lethal conditions from thermal discharges. Kerr(1953) subjected yearling fall-run Chinook salmon acclimated to 55-56T to instantaneous rises of up to 27°F for 3.5 to 5 minutes and found no mortality with a 25°F rise and reported a maximum temperature tolerance of 83°F.Boles (198 8)reviewed numerous studies conducted on thermal tolerance of salmonids and reported that the upper lethal temperature for long-term exposure among fingerling Chinook salmon in the Sacramento River to be 78.5°F, although higher temperatures can be tolerated for brief periods. Regarding thermal tolerances and preferences of steelhead,Myrick and Cech(2000)reported the incipient lethal temperatures for resident rainbow trout is approximately 78.8°F and upper critical thermal maxima approaches 87.8°F at high acclimation temperatures. Moyle (2002) states rainbow trout will survive temperatures approaching 82°F if they have been acclimated to the upper temperature and the water is saturated with oxygen. Leitritz and Lewis (1980)report yearlings and adults under hatchery conditions can withstand temperatures up to 78°F for short periods of time. The Santa Ynez River Technical Advisory Committee (2000)reported that young-of-the- year steelhead exposed to temperatures above 77°F in southern California's Santa Ynez River system were observed to be generally healthy and actively feeding. Studies of juvenile steelhead of the Central Valley have shown that steelhead may exhibit significant mortality under long-term exposure to temperatures exceeding 77°F, but they can tolerate temperatures up to 85°F for short periods of time(Myrick and Cech 2000). Based on the information provided above, anadromous salmonid emigrants actively swimming along the east margin of the river at or immediately downstream of the discharge outfall would be exposed to temperatures that could cause adverse effects and/or exceed thermal tolerances. In the event that these fish were to encounter the unfavorably high water temperatures while passing through the thermal plume,they would be expected to swim away from such areas as they continue their downstream movements. However,because the plume is relatively wide(maximum of approximately 150 feet)and is situated along the margin of the river, fish may not be able to immediately swim to cooler waters in the zone of passage. At the upstream head of the plume, exposure to the elevated temperatures would be sudden with little time to acclimate to the change. Conversely, exposure under such scenarios would be brief(e.g.,<30 minutes)due to river flow velocities in the portion of the channel affected by the plume and juvenile fish swimming speeds (see above). Emigrants that pass the location of the discharge outfall along the west margin of the river could swim through the zone of passage unaffected by the thermal plume. EDAW Manteca WQCF and Collection System Master Plans EIR Fisheries and Aquatic Resources 4.13-24 City of Manteca