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Near and Far Field Dilution Analysis of Manteca Discharge October 2006 <br /> • When the approaching flood tide does not include a period with less than 400 cfs <br /> downstream river flow, then the discharge is stopped when the downstream flow <br /> at the Mossdale Bridge station drops below 1,200 cfs. <br /> Using this method, the hours per day during which discharge was allowed were summed <br /> and the respective instantaneous discharge rates for the 9.87 MGD, 17.5 MGD and 27 <br /> MGD were determined. For example, if discharge were allowed for 12 hours during a <br /> day, the instantaneous discharge rate during those 12 hours would be 19.74 MGD or 30.5 <br /> cfs under the 9.87 MGD discharge scenario. <br /> The treatment plant discharge was tagged with a tracer concentration of 100 so that <br /> percent effluent could be computed. All other boundary concentrations were set to zero. <br /> Model results are analyzed for six locations shown in Figure 37. <br /> 1991 - 1992 Simulation Results <br /> Tidally averaged effluent concentrations for the 1991 -1992 simulations with 9.87 MGD, <br /> 17.5 MGD and 27 MGD Manteca discharge rates are plotted for six key locations in <br /> Figure 38 through Figure 43. August-September 1991 was simulated for model spin <br /> up,but results for this period are not shown. <br /> In Figure 38, at the Clifton Court intake,peak effluent concentrations occur during mid- <br /> December and mid-February. The lowest concentrations occur in early April. The <br /> effluent concentration for the 9.87 MGD case ranges from near zero to 1%. For the 17.5 <br /> MGD case, effluent concentration ranges near zero to 1.7%, and for the 27 MGD case, it <br /> ranges from 0.1%to 2.7%. <br /> In Figure 39, at the Delta Mendota Canal intake at Lindemann Road,peak effluent <br /> concentrations occur during mid-December and mid-February. The lowest <br /> concentrations occur in early May. The effluent concentration for the 9.87 MGD case <br /> ranges from less than 0.1%to 1.1%. For the 17.5 MGD case, effluent concentration <br /> ranges from 0.1%to 1.9%, and for the 27 MGD case, it ranges from 0.1% to 3%. <br /> In Figure 40, at the Contra Costa intake in Rock Slough,peak effluent concentrations <br /> occur during mid-December. The lowest concentrations occur in mid-April. The effluent <br /> concentration for the 9.87 MGD case ranges from near zero to 0.2%. For the 17.5 MGD <br /> case, effluent concentration ranges near zero to 0.3%, and for the 27 MGD case, it ranges <br /> from near zero to 0.5%. <br /> In Figure 41, at the Contra Costa intake in Old River, peak effluent concentrations occur <br /> during mid-December and mid-February. The lowest concentrations occur in early April. <br /> The effluent concentration for the 9.87 MGD case ranges from near zero to 0.3%. For <br /> the 17.5 MGD case, effluent concentration ranges near zero to 0.5%, and for the 27 MGD <br /> case, it ranges from near zero to 0.8%. <br /> In Figure 42, at San Joaquin River at Light 18, peak effluent concentrations occur during <br /> early November. The lowest concentrations occur in early April. The effluent <br /> concentration for the 9.87 MGD case ranges from near zero to 0.9%. For the 17.5 MGD <br /> case, effluent concentration ranges from near zero to 1.6%, and for the 27 MGD case, it <br /> ranges from less than 0.1%to 2.4%. <br /> 42 <br />