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The results of the present analysis indicate that TSS concentration in the San Joaquin River will Aluminum <br /> slightly decrease with increasing WQCF effluent discharge,thus lessoning the concentration of <br /> suspended material in the river and complying with the narrative water quality objective. Data Availability: Manteca WQCF NPDES self-monitoring data from the San Joaquin River at <br /> Furthermore,NPDES permit effluent limitations will be sufficiently stringent to provide the R-1(just upstream of the WQCF discharge)corresponding to dry/below normal water years were <br /> intended level of protection to the beneficial uses of the San Joaquin River. used to calculate an estimated impact of WQCF effluent total aluminum in the San Joaquin River <br /> under critical(600 cfs)and dry/below normal(1250 cfs)river flows at a permitted discharge of <br /> Evaluation: Because WQCF effluent TSS concentration is lower than the ambient TSS 9.87 MGD(ADWF)and at proposed discharges of 17.5 MGD(ADWF)and 27 MGD(ADWF). <br /> concentration in the San Joaquin River,increasing WQCF effluent discharge will decrease Improved WQCF treatment processes are projected to produce treated effluent having an average <br /> receiving water concentrations. TSS mass loading to the river is projected to be slight relative to total aluminum concentration of 150µg/L. <br /> existing in-stream loads. Additionally,with a high-rate activated sludge process,an easily <br /> filterable secondary effluent will be produced. Following tertiary filtration in accordance with Results: The effect of an increase in WQCF discharge from 9.87 MGD(ADWF)to 27 MGD <br /> Title 22 standards and UV disinfection conforming to National Water Research Institute(NWRI) (ADWF)is appropriately addressed in the receiving water at well-mixed conditions downstream <br /> guidelines,effluent concentrations of suspended solids will be less than 10 mg/L. of the discharge. During critical and dry/below normal San Joaquin River flow conditions,an <br /> increase in WQCF effluent discharge will slightly decrease total aluminum concentration in the <br /> Table 12: Estimated Impact of Total Suspended Solids from WQCF Discharge in the San Joaquin San Joaquin River downstream of the discharge as shown in Figure 7 and Table 13. The <br /> River at WQCF R-3 column chart also indicates that estimated concentrations of total aluminum in the river far <br /> exceed the U.S.EPA chronic ambient water quality criterion(87µg/L)for the metal(USEPA, <br /> Total Suspended Solids(TSS) San Joaquin River Manteca WQCF Effluent 2002),which is often used by the Regional Water Board to interpret the narrative toxicity <br /> R-1 50"%concen. * 25,7/L m Flowrate(cfs) Flowrate(MGD ADWF) <br /> concen.(mg/L)*) objective contained in the Basin Plan. Current permitted WQCF effluent limitations for total <br /> Projected effluent concen.(mg/L) 10 600 1250 9.87 17.5 27 aluminum include a monthly average of 71µg/L and a daily maximum of 140µg/L. Past water <br /> Est.mass loading(lbs/day) 83,114 173,154 823 1,460 2,252 quality data collected by the WQCF indicate that aluminum concentrations in the effluent—and <br /> Est.downstream R-3 river concentration(mg/L)at 600 cfs 25.3 25.0 24.7 the San Joaquin River—exceed these limitations. Therefore,the City is exploring various <br /> Est.downstream R-3 river concentration(mg/L)at 1250 cfs 25.5 25.4 25.2 compliance options to meet these effluent limits. The City has been granted the opportunity by <br /> •50"percentile statistic calculated using the following data set: the Regional Water Board to assess compliance with the aluminum effluent limits using the acid <br /> Data Period:November 2005—July 2006;Sample Size,n=16;Percent Detected Data=100% soluble method for aluminum analysis and/or by conducting a Water Effects Ratio(WER)to <br /> develop a site specific objective(SSO). Based on the data collected to date,the acid-soluble <br /> measurement does not appear to be useful or applicable to compliance measurement because the <br /> analysis of the acid-soluble portion of a total metal commonly does not result in significantly <br /> lower values of the total metal when compared to the analysis of the metal without acidification. <br /> In contrast,the City's aluminum WER study(City of Manteca,2007)recommended a WER of <br /> 22.7 for direct adjustment of the chronic objective. This WER would also be applicable to the <br /> corresponding acute objective. The 87 pg/L U.S.EPA chronic criterion is based on toxicity tests <br /> using striped bass and brook trout in water with pH between 6.5 and 6.6 and hardness <br /> concentrations(as CaCO3)of less than 10 mg/L(striped bass)and 12.3 mg/L(brook trout). <br /> WER studies conducted since this time and anecdotal evidence support the conclusion that <br /> aluminum is substantially less toxic at the higher pH and hardness values that are typical in the <br /> San Joaquin River. This conclusion is supported by the City's WER study,which noted only one <br /> case when there was a negative response to an aluminum-dosed environmental sample(effluent, <br /> upstream,or simulated downstream). Additionally,studies completed by other San Joaquin <br /> River dischargers have indicated that WERs exceeding 20 are scientifically defendable. A slight <br /> increase in total aluminum mass loading to the river is also projected. <br /> City of Manteca Antidegradation Analysis 37 June 2007 City of Manteca Antidegradation Analysis 38 June 2007 <br />