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Most importantly,the present analysis shows that projected,median EC in the San Joaquin River Ammonia <br /> is below both seasonally-relevant water quality objectives. The City's potable water supply is <br /> expected to improve in quality,with respect to EC,as compared to pre-August 2005 conditions Data Availability: Manteca WQCF NPDES self-monitoring data from the San Joaquin River at <br /> due to the blending of surface water from the South County Water Supply Program with the R-1(just upstream of the WQCF discharge)corresponding to dry/below normal water years were <br /> City's groundwater. The blending of surface water with groundwater for the potable water used to calculate an estimated impact of WQCF effluent ammonia(as nitrogen)in the San <br /> supply has significantly decreased the EC measured in WQCF effluent when comparing pre-and Joaquin River under critical(600 cfs)and dry/below normal(1250 cfs)river flows at a permitted <br /> post-August 2005 plant effluent measurements(LWA,2006b). discharge of 9.87 MGD(ADWF)and at proposed discharges of 17.5 MGD(ADWF)and 27 <br /> MGD(ADWF). Improved WQCF treatment processes are projected to produce treated effluent <br /> Table 14: Estimated Impact of Electrical Conductivity during April through August from WQCF having an average ammonia(as nitrogen)concentration of 1.5 mg/L. <br /> Discharge in the San Joaquin River at WQCF R-3 Results: The effect of an increase in WQCF discharge from 9.87 MGD(ADWF)to 27 MGD <br /> Electrical Conductivity(April-August) San Joaquin River Manteca WQCF Effluent (ADWF)is appropriately addressed in the receiving water at well-mixed conditions downstream <br /> m Flowrate(cis) Flowrate(MGD ADWF) of the discharge. Due to the seasonal nexus of U.S.EPA ambient water quality criteria for <br /> R-1 50 %EC(µmhos/cm)* 574.9 ammonia(as nitrogen),available ammonia data were divided into two groups for the purpose of <br /> Projected effluent EC(µmhos/cm) 825 600 1 1250 9.87 17.5 27 the present near-field analysis:a June through September data set,and an October through May <br /> Est.downstream R-3 river electrical conductivity(µmhos/cm)at 600 cfs 581.1 585.7 591.2 data set. During critical and dry/below normal San Joaquin River flow conditions,an increase in <br /> Est.downstream R-3 river electrical conductivity(µmhos/cm)at 1250 cfs 577.9 580.2 583.0 WQCF effluent discharge will produce a moderate increase in ammonia(as nitrogen)levels in <br /> *50"percentile statistic calculated using the following data set: the San Joaquin River downstream of the discharge during June through September relative to its <br /> Data Period:April-August 2002,April-May 2004;Sample Size,n=8;Percent Detected Data=100% seasonal objective of 0.62 mg/L,and will produce a slight increase in ammonia(as nitrogen) <br /> levels in the river during October through May relative to its seasonal objective of 5.62 mg/L. <br /> The more distinct increase in ammonia levels in the river during the June through September <br /> time period is due to the higher ambient levels of ammonia(as nitrogen)measured in the San <br /> Table 15: Estimated Impact of Electrical Conductivity during September through March from <br /> WQCF Discharge in the San Joaquin River at WQCF R-3 Joaquin River at R-1 during this time period in Conjunction with the more stringent chronic <br /> ammonia objective in effect from June through September. These incremental increases in river <br /> Electrical Conductivity(September-March) San Joaquin River Manteca WQCF Effluent ammonia(as nitrogen)concentrations and mass loadings observed when evaluating the June <br /> R-1 50th%EC(µmhos/cm)* 785.9 Flowrate(cfs) Flowrate(MGD ADWF) through September(associated with the EPA chronic ammonia criterion)and October through <br /> Projected effluent EC(µmhos/cm) 825 600 1 1250 9.87 17.5 27 May(associated with the EPA acute ammonia criterion)time periods are shown in Figure 10 <br /> Est.downstream R-3 river electrical conductivity(µmhos/cm)at 600 cfs 786.9 787.6 788.4 and Table 16,and Figure Hand Table 17,respectively. <br /> Est.downstream R-3 river electrical conductivity(µmhos/cm)at 1250 cfs 786.4 786.7 787.2 <br /> '50'"percentile statistic calculated using the following data set: Ammonia as Nitrogen(June-Sept.) <br /> Data Period:Jan.-Mar.2002,Sept.-Dec.2002,Sept.2004;Sample Size,n=8;Percent Detected Data=100% <br /> 1 <br /> J <br /> 0.8 SJR Flows <br /> c 0.6- �600 cfs <br /> 1250 cfs <br /> 0.4 -Chronic WQO <br /> m <br /> � 0.2 <br /> 0 <br /> U <br /> 0- <br /> 9.87 17.5 27 <br /> WQCF Effluent Flow Rate(MGD) <br /> Figure 10: Projected Change in San Joaquin River Ammonia(as Nitrogen)Concentration at <br /> WQCF R-3 during June through September with increasing WCQF Effluent Flowrate <br /> City of Manteca Antidegradation Analysis 43 June 2007 City of Manteca Antidegradation Analysis 44 June 2007 <br />