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Methylene Blue Active Substances(MBAS) the current permitted discharge of 9.87 MGD(ADWF)to the proposed 27 MGD(ADWF). <br /> Projected,median MBAS concentrations in the San Joaquin River are well below the Title 22 <br /> Data Availability: A limited methylene blue active substances(MBAS)receiving water data set Secondary MCL standard. <br /> featuring all non-detected R-1 data was available for this analysis. To that end,an estimated <br /> MBAS concentration in the San Joaquin River at R-1(just upstream of the WQCF discharge) Evaluation: The incremental change in MBAS concentration and mass loading in the San <br /> corresponding to dry/below normal water years was used to calculate a projected impact of Joaquin River due to an increase in WQCF effluent discharged from the current permitted rate <br /> WQCF effluent MBAS in the San Joaquin River under critical(600 cfs)and dry/below normal (9.87 MGD(ADWF))to the proposed rate(27 MGD(ADWF))is slight. Additionally,projected <br /> (1250 cfs)river flows at a permitted discharge of 9.87 MGD(ADWF)and at proposed MBAS concentrations in the San Joaquin River are well below the Title 22 Secondary MCL of <br /> discharges of 17.5 MGD(ADWF)and 27 MGD(ADWF). Improved WQCF treatment 500 pg/L. <br /> processes are projected to produce treated effluent having an average MBAS concentration of <br /> 160 pg/L. Table 23: Estimated Impact of Methylene Blue Active Substances from WQCF Discharge in the <br /> San Joaquin River at WQCF R-3 <br /> Results: The effect on an increase in WQCF discharge from 9.87 MGD(ADWF)to 27 MGD <br /> (ADWF)is appropriately addressed in the receiving water at well-mixed conditions downstream Methylene Blue Active Substances(MBAS) San Joaquin River Manteca WQCF Effluent <br /> of the discharge. During critical and dry/below normal San Joaquin River flow conditions,an R-1 estimated concen.(gg/L)* 20 Flowrate(cfs) Flowrate(MGD ADWF) <br /> increase in WQCF effluent discharge will slightly increase MBAS concentration in the San Projected effluent concen.(pg/L) 1 160 600 1250 9.87 17.5 27 <br /> Joaquin River,relative to its Title 22 Secondary MCL criterion,downstream of the discharge as Est.mass loading(lbs/day) 65 135 13.2 23.4 36.0 <br /> shown in Figure 17 and Table 23. The R-1 ambient MBAS concentration employed in the <br /> present analysis was estimated using the median method detection limit(MDL)associated with Est.downstream R-3 river concentration(pg/L)at 600 cfs 23.5 26.1 29.1 <br /> the non-detected data. The median MDL for MBAS from the City's NPDES self-monitoring Est.downstream R-3 river concentration(pg/L)at 1250 cfs 21.7 23.0 24.5 <br /> data is 20µg/L. A slight increase in MBAS mass loading to the river is also projected. •Statistic derived from the foiiming data set: <br /> Data Period:January 2002—December 2002;Sample Size,n=12;Percent Detected Data=0 <br /> Methylene Blue Active Substances(MBAS) <br /> 600 <br /> J <br /> 500 SJR Flows <br /> 3 <br /> 0 400 600 cfs <br /> 300 1250 cfs <br /> 200 —WOO <br /> c 100 <br /> U <br /> 0- <br /> 9.87 17.5 27 <br /> WQCF Effluent Flow Rate(MGD) <br /> Figure 17: Projected Change in San Joaquin River Methylene Blue Active Substances <br /> Concentration at WQCF R-3 with increasing WQCF Effluent Flowrate <br /> Comparison to Water Quality Objective: The California Code of Regulation,Title 22 <br /> Secondary MCL criterion for MBAS,incorporated into the Basin Plan by reference,is 500 pg/L. <br /> Estimated concentrations of MBAS in the San Joaquin River under critical and dry/below normal <br /> flow conditions show a slight increase,relative to the Title 22 Secondary MCL,with an increase <br /> in WQCF effluent discharge from 9.87 MGD(ADWF)to 27 MGD(ADWF). The incremental <br /> change in MBAS concentration in the river is slight when increasing the WQCF discharge from <br /> City of Manteca Antidegradation Analysis 57 June 2007 City of Manteca Antidegradation Analysis 58 June 2007 <br />