ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Using the estimate of water quality within the Delta without a WQCF discharge(C3,n3 wQcF),the Table 38: Median Percent Contribution of WQCF Effluent at Select Locations within the Delta for model results for the contribution of WQCF effluent from project scenarios(f= Dry/Below Normal Water Years percentage/100%)may be used in conjunction with projected future WQCF effluent quality Percent Contribution for WQCF ADWF(%) (Cefr)to estimate the future Delta water quality(CS,I„re). The approach is most applicable to EC, Location 3.5(')MGD 9.87 MGD 17.5 MGD 27 MGD as it is a conservative parameter. The approach is also used for nitrate and DOC,both of which undergo reactions and transformations as they travel downstream and through the Delta, SWP Clifton Court Intake 0.0311 0.0867 0.1534 0.2365 therefore the results presented here overestimate the WQCF contribution ofthese constituents to CVP DMC Intake 0.0839 0.2365 0.4193 0.6469 the Delta. CCWD Intake at Rock Slough 0.0025 0.0068 0.0119 0.0184 CM--Cs n.WocF+f'(Can-Caan.WocF) CCWD Intake at Old River 0.0102 0.0281 0.0495 0.0762 Results for the three constituent are tabulated below. San Joaquin River at Light 18 0.0540 0.1514 0.2681 0.4133 Stockton Turning Basin 0.2891 0.8152 1.4454 2.2300 Results: The results from the far-field analysis are presented in Tables 40 to 45. Two tables are (1)For the modeled dry/below normal water year(2001/2002)the WQCF ADWF was 3.5 MGD(ADWF). presented for each constituent representing the results for the critical and dry/below normal water year conditions. The observed water quality for each location is listed under the 2.1 MGD (ADWF)scenario for critical water year conditions and 3.5 MGD(ADWF)for dry/below normal Historic WQCF effluent quality is listed in Table 39. Only total dissolved solids(TDS)data are water year conditions. Each table includes a project build-out percent change in concentration, available for the 1991/1992 historic WQCF effluent quality. To estimate the EC values,the calculated by comparing the calculated concentrations at a location corresponding to the WQCF historic TDS values are scaled by the EC/TDS ratio measured during the WQCF's 13267 operating at ADWFs of 9.87 MGD and 27 MGD. monitoring. The 13267 data are used to estimate the drylbelow normal water year value. The EC results are presented in Tables 40 and 41,corresponding to critical and dry/below normal future EC is derived from the Master Plan Update(Nolte,2007). water years,respectively. Monitoring data for EC are not available for the San Joaquin River at Navigation Light 18 and the Stockton Ship Channel Turning Basin for critical water years and Table 39: WQCF Typical Effluent Quality for Historic and Future Conditions the Delta Mendota Canal intake and Contra Costa Water District intake at Old River for dry/below normal water years. For both water year types,the calculated change in EC at the Critical WY Dry WY Proposed selected sites is typically less than 1µmho/cm and no greater than 2µmho/cm when the WQCF Parameter 1991/1992 2001/2002 Project ADWF is increased from 9.87 to 27 MGD. ADWF(MGD) 2.1 3.5 17.5/27 EC(pmhos/cm) 1,2031'1 1,143(2) 825(3) Table 40: Median Electrical Conductivity(EC)at Select Locations within the Delta for Project DOC(mg/L)(4) 9.0 9.0 9.0 Scenarios under Critical Water Year Conditions Nitrate(mg/L) 0.8 4.6 5.0 EC(pmhos/cm)for WQCF ADWF(MGD) AM (1)TDS value of 642 mg/L scaled by ECfrDS ratio of(1,143/610). Location 0.00) 2.1(2) 9.87 17.5 27 (pmhos/cm) (2)Mean EC value from 13267 monitoring. (3)City of Manteca WQCF Master Plan Update January 2007:Table 2-4-Schedule D(Nolte,2007). SWP Clifton Court Intake 546 547 547 547 547 <1 (4)Data only available from August 2005 to April 2006. CVP DMC Intake 593 593 594 594 595 1 CCWD Intake at Rock Slough 599 599 599 599 599 <1 Historic ambient water quality conditions at six Delta locations were calculated using data CCWD Intake at Old River 578 578 578 578 579 1 available from several monitoring programs(see Table 7 and Table 8). Representative water San Joaquin River at Light 18 No Data quality estimates for EC,DOC,and nitrate for each location and modeled water year are Stockton Turning Basin No Data presented in the following Results subsection in Tables 40 through 45. (1)Estimated water quality at the selected location without WQCF effluent. Using the representative water quality at each location in the Delta(Cobs),the WQCF effluent (2)The WQCF ADWF during the modeled critical water year was 2.1 MGD.Values listed represent the median observed at the quality Cefr for the modeled water ears,and the estimated WQCF percent effluent contribution location. �l tY( ) Y Q p (3)Incremental change between build-out(27 MGD(ADWF))and current permitted condition(9.87 MGD(ADWF)). (f=percentage/100%),a mass balance equation can be used to estimate the water quality in the Delta without a discharge at Manteca(Cs WQCF)- wocr- Cse�s Cobs-f'Ceff - 0_f) City of Manteca Antidegradation Analysis 91 June 2007 City of Manteca Antidegradation Analysis 92 June 2007