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Mercury Evaluation: The incremental change in total mercury concentration in the San Joaquin River <br /> due to an increase in WQCF effluent discharged from the current permitted rate(9.87 MGD <br /> Data Availability: Manteca WQCF NPDES self-monitoring data from the San Joaquin River at (ADWF))to the proposed rate(27 MGD(ADWF))is slight and below the magnitude of change <br /> R-1(just upstream of the WQCF discharge)corresponding to dry/below normal water years were that could be reliably measured in the field. Additionally,projected,median total mercury <br /> used to calculate an estimated impact of WQCF effluent total mercury in the San Joaquin River concentrations in the San Joaquin River are well below the CTR Human Health(water and <br /> under critical(600 cfs)and dry/below normal(1250 cfs)river flows at a permitted discharge of organisms)criterion of 0.05 itg/L. It should be recognized that the estimated mass loading <br /> 9.87 MGD(ADWF)and at proposed discharges of 17.5 MGD(ADWF)and 27 MGD(ADWF). (lbs/day)of total mercury in the San Joaquin River at a WQCF effluent flowrate of 27 MGD <br /> Improved WQCF treatment processes are projected to produce treated effluent having an average (ADWF)does produce a load(0.82 lbs/year)greater than the currently permitted 0.69 lbs/year <br /> total mercury concentration of 0.01 pg/L. based on a WQCF treatment design capacity of 8.11 MGD(ADWF). With respect to the <br /> Results: The effect of an increase in WQCF discharge from 9.87 MGD(ADWF)to 27 MGD Sacramento-San Joaquin Delta Mercury TMDL,the establishment of a future waste load <br /> (ADWF)is appropriately addressed in the receiving water at well-mixed conditions downstream allocation(WLA)and future mass limit for the WQCF will need to consider all existing mercury <br /> of the discharge. During critical and dry/below normal San Joaquin River flow conditions,an inputs in the watershed in order to develop an appropriate WLA that provides the intended level <br /> increase in WQCF effluent discharge will slightly increase total mercury concentration in the of protection to the beneficial uses of the San Joaquin River. Upon review of the methylmercury <br /> San Joaquin River,relative to its CTR objective,downstream of the discharge as shown in data generated from the 2004-2005 Central Valley Clean Water Agency Mercury Study <br /> Figure 20 and Table 26. A slight increase in total mercury mass loading to the river is also (Pirondini,2006),it is anticipated that future methylmercury levels in WQCF tertiary treated <br /> projected. effluent should not exceed,on average,the 0.06 ng/L methylmercury implementation goal set <br /> forth in the draft Sacramento-San Joaquin Delta Methylmercury TMDL(CVRWQCB,2006a). <br /> Mercury,Total Table 26: Estimated Impact of Total Mercury from WQCF Discharge in the San Joaquin River at <br /> WQCF R-3 <br /> J 0.06 Mercury,Total San Joaquin River Manteca WQCF Effluent <br /> 0.05 SJR Flowsm o/ Flowrate(cis) Flowrate(MGD ADINF) <br /> 3 R-1 50 concen.(µg/L)* 0.005 <br /> `0 0.04 600 cfs Projected effluent concen.(µg/L) 0.01 600 1250 9.87 17.5 27 <br /> 0.03 �1250 cfs Est.mass loading(lbs/year) 6.35 13.23 0.30 0.53 0.82 <br /> d 0.02 WQQ Est.downstream R-3 river concentration(µg/L)at 600 cfs 0.005 0.006 0.006 <br /> u <br /> 0 0.01 Est.downstream R-3 river concentration(µg/L)at 1250 cfs 0.005 0.005 0.006 <br /> 0 '501"percentile statistic calculated using the following data set: <br /> 9.87 17.5 27 Data Period:January 2002-September 2004;Sample Size,n=14;Percent Detected Data=100% <br /> WQCF Effluent Flow Rate(MGD) <br /> Figure 20: Projected Change in San Joaquin River Total Mercury Concentration at WQCF R-3 with <br /> increasing WQCF Effluent Flowrate <br /> Comparison to Water Ouality Objective: The CTR Human Health(water and organisms) <br /> objective for total mercury as it applies to the San Joaquin River is 0.05µg/L. Estimated <br /> concentrations of total mercury in the San Joaquin River under critical and dry/below normal <br /> flow conditions show a slight increase,relative to the CTR Human Health objective,with an <br /> increase in WQCF effluent discharge from 9.87 MGD(ADWF)to 27 MGD(ADWF). The <br /> incremental change in total mercury concentration in the river is slight when increasing the <br /> WQCF discharge from the current permitted discharge of 9.87 MGD(ADWF)to the proposed <br /> 27 MGD(ADWF). Projected,median total mercury in the San Joaquin River are well below the <br /> CTR Human Health(water and organisms)objective. <br /> City of Manteca Antidegradation Analysis 63 June 2007 City of Manteca Antidegradation Analysis 64 June 2007 <br />