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Near and Far Field Dilution Analysis of Manteca Discharge October 2006 <br /> Table 2 Summary of percent cross-sectional area elevated more than 1°F during the winter, <br /> historical low flow,intermittent discharge simulations. <br /> % cross-sectional area elevated more <br /> Distance than 1° F <br /> downstream of 9.87 MGD on 28 MGD on <br /> discharge (ft) December 6 December 3 <br /> 25 7 15 <br /> 125 8 35 <br /> 250 9 41 <br /> 450 16 47 <br /> 1,000 22 48 <br /> 1,500 0 51 <br /> Temperature Differential Sensitivity Analysis <br /> Sensitivity analysis simulations were performed for fall, historical low flow conditions to <br /> determine the amount of cooling of effluent temperatures that would be required to <br /> achieve less than 25% of the river cross-section elevated more than 1°F for the 27 MGD <br /> discharge rate with a side bank discharge. <br /> For the fall historical low flow intermittent discharge sensitivity analysis simulations, <br /> October 2002 stage at the Old River at Head CDEC station was applied to the <br /> downstream boundary. Temperature and EC at the downstream boundary were computed <br /> within the model. Temperature and EC from the Vernalis CDEC station for this period <br /> were applied at the upstream boundary. San Joaquin River flows averaging 600 cfs, <br /> representative of historical extreme low conditions, were applied at the upstream <br /> boundary. An intermittent Manteca daily discharge rate of 27 MGD was used. <br /> The Manteca discharge was assigned for different temperatures to determine the effluent <br /> temperature reduction that would be required to achieve less than 25% of the river cross- <br /> section elevated more than P F. The observed effluent temperature during this time is <br /> estimated to be 76°F based on analysis of valve pit temperatures. Heat exchange was <br /> computed using heat budget parameters calibrated for this period. <br /> Table 3 shows peak cross-sectional area percentages elevated above 1°F for four <br /> different effluent temperatures. Results indicate that a reduction of approximately 11°F <br /> would be required to reduce the cross-sectional area impacted to less than 25%. <br /> 31 <br />