ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Table 10: Projected WQCF Effluent Quality after Phase III Expansion 1. Projected WQCF effluent quality after Phase III expansion(see Table 10); Constituent Units Projected Effluent Qualityt'I 2. Median(50"'percentile)ambient San Joaquin River concentrations calculated from data sets comprised of water quality measurements collected during dry and above normal Biochemical Oxygen Demand(BOD) mg/L 7 water years; Total Suspended Solids(TSS) mg/L <10 Total Coliform MPN/100 mL <2.2 3. Current permitted and proposed future WQCF effluent flowrates:9.87,17.5,and 27 MGD(ADWF);and Turbidity NTU <2 Settleable Solids mg/L 0.1 4. Average late summer/early fall San Joaquin River flows observed during historic critical Chlorine Residual mg/L 0.01 (1992)and dry(2002)water years. Oil and Grease mg/L 2.1 Aluminum µg/L 150 The estimated near-field water quality impacts were calculated using the following mass balance Electrical Conductivity(EC) µmhos/cm 825 equation: Ammonia(as N) mg/L 1.5C p ps„Qam + C �x 1.55 aownsneem= ( )(Q ) ( g)(Q ) Arsenic µg/L 8 Cx . Qunso-eam+(Qeg 1 55) Copper µg/L 7 Cyanide µg/L 1 Where Cd.._,,_=San Joaquin River concentration,downstream of discharge at R-3 Iron µg/L 50 C nstremn=San Joaquin River concentration,upstream of discharge at R-1 Manganese µg/L 10 C ff=WQCF effluent concentration Methylene Blue Active Substances(MBAS) µg/L 160 Q„Pstream=San Joaquin River flow(cfs),upstream of discharge at Vernalis Nitrate(as N) mg/L 5 Q fl=WQCF effluent flow(MGD) Nitrite(as N) mg/L 1 Bis(2-ethylhexyl)phthalate µg/L 3.48 Bromodichloromethane µg/L Non-detect in effluent(<0.2µg/L) Projected average effluent concentrations resulting from proposed improvements to the WQCF treatment process were used to estimate future impacts of the WQCF discharge on San Joaquin Mercury µg/L Non-detect in 0.010effluent(<0.3µg/L) River water quality. Median(50d'percentile)receiving water concentrations were calculated Mercury µg/L 0.010 using data collected at WQCF R-1,where possible. The median concentration is used for the 2,4,6-Trichlorophenol µg/L 3.28 receiving water because the analysis is strictly based on evaluating the change in receiving water (t)All concentrations represent projected mean values taken from City of Manteca WQCF Master Pian Update(Nolte,2007. quality. Ambient R-1 concentrations serve as a basis for comparing the magnitude of future change in receiving water quality due to the project. Near-Field Impacts Calculations Constituents were evaluated under both critical and dry/below normal flow conditions corresponding to critical and dry/below normal water years,respectively. For the critical water The near-field water quality impacts assessment evaluates the effects of increasing WQCF year,a San Joaquin River flowrate of 600 cfs was chosen as representative of extremely low discharge from the permitted 9.87 MGD(ADWF)to a proposed 27 MGD(ADWF)effluent flow conditions based on historic monthly average flows calculated for the San Joaquin River at flowrate. Because the construction of WQCF improvements is scheduled to occur in two phases, Vernalis during Fall of 1991 and 1992;both years classified as critical by the DWR hydrologic with the completion of the first phase resulting in a discharge capacity of 17.5 MGD(ADWF), classification scheme(LWA,2006a). Similarly,a flow of 1,250 cfs was chosen as representative water quality impacts were also estimated for this incremental discharge stage. Near-field effects of dry/below normal water year flow conditions based on San Joaquin River at Vernalis flows on San Joaquin River water quality will occur between the point of discharge and WQCF measured during the Fall of 2002;a year classified as a dry water year(LWA,2006a). Due to monitoring location R-3(approximately 1-mile downstream of the WQCF outfall;see Figure 2) agreements currently in place to provide water for migration of anadromous fish species in the where advanced treatment effluent and ambient river water are well-mixed as determined by Delta(1995 Bay-Delta Plan;SWRCB,1995;and the Revised Water Right Decision 1641; recent hydrodynamic modeling conducted by the City(RMA,2006). Near-field water quality SWRCB,2000),as well as future San Joaquin River flow objectives that may be set forth in a impacts are estimated using the following four parameters which characterize WQCF effluent future Bay-Delta Plan,future San Joaquin River flows should be similar to or greater than those and San Joaquin River water quality: observed during historic dry water years during future rainfall-limited years. Evaluating changes in San Joaquin River water quality due to an increase in WQCF effluent discharge under critical City of Manteca Antidegradation Analysis 31 June 2007 City of Manteca Antidegradation Analysis 32 June 2007