ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Data collected during both critical and drylbelow normal water years at far-field Delta monitoring locations were available for use in the far-field impacts assessment. However,these San Joaquin Valley Water Year ambient Delta water quality data sets are often limited and inconsistent or patchy in terms of the Hydrologic Classification: 1990-2006 suite of constituents evaluated at any given monitoring site,and thus collectively produce a geographical and chronological mosaic of Delta water quality conditions that provides an ■San Joaquin River Unimpaired Runoff IN Water Year Index incomplete picture of far-field water quality impacts due to an increase in WQCF discharge. The 14 only parameters with sufficient data to produce a reasonable depiction of far-field impacts during E critical and dry/below normal water years due to an increase in WQCF discharge are electrical 1z conductivity(EC),dissolved organic carbon(DOC),and nitrate(as nitrogen). EC,DOC,and >° 10 nitrate(as nitrogen)are general indicators of water quality and are important parameters used by 0 6 water purveyors to assess treatment requirements of raw water. 'a E 6 NEAR-FIELD METHODOLOGY d a 4LL The near-field effects on water quality of the current permitted WQCF design capacity(9.87 E 2 MGD(ADWF))and the proposed WQCF design capacity(27 MGD(ADWF))are compared M 0MEN using a mass balance equation. Using projected effluent quality and available ambient San 1990 1991 1992 1993 1094 1995 1996 1997 1996 7999 2000 2007 2002 2003 2004 2005 2006 Joaquin River water quality(measured at R-1 and the Interstate 5 Mossdale Bridge)and flow data(measured at Vernalis),a mass balance was performed to assess the effect of WQCF C C C W C W W W W AN AN D D BN D w w discharge on downstream concentrations of pollutants with an increase in effluent flowrate. Year and water Year Hydrologic Classification Based on recent hydrodynamic modeling(RMA,2006),WQCF effluent and San Joaquin River water are considered well-mixed approximately 1-mile downstream of the WQCF outfall,near the WQCF R-3 self-monitoring site. The instantaneous effluent flowrates from timed discharge Notes: operation are not evaluated in the analysis because impacts on receiving water are being 1.The data presented above were generated by the California Department of Water Resources evaluated sufficiently far downstream of the discharge,effectively evaluating the average daily (see http://cdec.water.ca.gov/cgi-progs/iodirNVSIHIST). These indices have been used operationally by DW R for planning and managing of water supplies since 1995,and are defined in SW RCB effluent flowrate on the receiving water conditions(RMA,2006). The three near-field WQCF Decision 1641(see http://www.waterrights.ca.gov/baydelta/dl641.htm). discharge scenarios for which ambient San Joaquin River concentrations downstream of the 2.A water year extends from Oct 1-Sep 30. WQCF discharge are estimated include: 3.Unimpaired runoff represents the natural water production of a river basin,unaltered by upstream diversions,storage,or export of water to or import of water from other basins. • 9.87 MGD(ADWF)—treatment capacity at completion of Phase III—Schedule D 4.San Joaquin River Runoff is the sum of Stanislaus River inflow to New Melones Lake,Tuolumne improvements,August 2007 River inflow to New Don Pedro Reservoir,Merced River inflow to Lake McClure,and San Joaquin River inflow to Millerton Lake. • 17.5 MGD(ADWF)—proposed intermediate design flow at end of first phase(Phase IV) 5.San Joaquin Valley Water Year Index=0.6*Current Apr-Jul Runoff in(maf)+0.2*Current of WQCF expansion Oct-Mar Runoff in(maf)+0.2*Previous Water Year's Index[if the Previous Water Year's Index exceeds 4.5,then 4.5 is used). • 27 MGD(ADWF)—proposed final build-out design flow at end of second phase(Phase 6.San Joaquin Valley Water Year Hydrologic Classification: V)of WQCF expansion Year Type: Water Year Index: Near-field analyses were conducted for the 15 parameters specified in Table 7. Data used in the W=Wet Year Equal to or greater than 3.8 AN=Above Normal Greater than 3.1,and less than 3.8 near-field analysis came from the various monitoring programs presented in Table 8. It should BN=Below Normal Greater than 2.5,and equal to or less than 3.1 be noted that limited receiving water data were available for all parameters considered for near- D=Dry Greater than 2.1,and equal to or less than 2.5 field impact assessments. Projected WQCF effluent quality to be achieved at the completion of C=Critical Equal to or less than 2.1 Schedule D WQCF improvements(expected August 2007,when the facility is expected to realize its current permitted design capacity of 9.87 MGD(ADWF)),and used in the near-field water quality impacts assessment is presented in Table 10(Nolte,2007). Figure 4: San Joaquin Valley Unimpaired Runoff and Water Year Classification:1990—2006 City of Manteca Antidegradation Analysis 29 June 2007 City of Manteca Antidegradation Analysis 30 June 2007