ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Table 33: Initial Total Ultimate Oxygen The calculated,minimum DO concentration for no discharge,9.87 MGD(ADWF),17.5 MGD Demand,L;,for Streeter-Phelps Analysis (ADWF),and 27 MGD(ADWF)are plotted in Figure 25. The incremental change in minimum Case(MGD ADWF) Initial TUOD(mg/L) river DO concentrations is limited to less than 0.1 mg/L between the currently permitted discharge rate of 9.87 MGD(ADWF)and projected build-out of 27 MGD(ADWF). It would be R-1 13.7 unlikely to be able to measure the difference in San Joaquin River DO as the WQCF effluent rate 9.87 13.9 is increased from 9.87 MGD(ADWF)to 27 MGD(ADWF). 17.5 14.0 27 14.1 9 Results Dissolved Oxygen:The results generated from the Streeter-Phelps model can only be utilized to evaluate the relative impact of increasing the WQCF discharge rate. The model does d 8- -not account for tidal cycles,inputs to the river downstream of the WQCF,sediment oxygen 7� demand,daylight oxygen generation,etc.and should not be used to estimate future absolute DO concentrations. The model does account for the consumption of oxygen as organic matter and E ammonia are oxidized;and replenishment of oxygen from the atmosphere. The Streeter-Phelps 7 model should only used to evaluate the incremental impact on DO concentrations in the San T Joaquin River as the WQCF discharge rate is increased. x 0 Monthly results of the Streeter-Phelps analysis are listed in Table 34. The location of the critical 0 6 oxygen condition will vary from immediately at the point of discharge to several days float time H -Mn.Do No Dacharge downstream of the discharge. Because the analysis does not included any additional inputs to the Mo.DO 9.87 MGD -M(-Mo.DO 17.5 MGD river downstream of the discharge,as the critical position moves further downstream the value of t Mn.DO 27 MGD the absolute minimum DO concentration will be less precise. However,the incremental change 5 in DO with implementation of the project can be well estimated by the model. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Table 34: Streeter-Phelps Analysis Results for Project WQCF Flowrates(ADWF) 9.87 MGD 17.5 MGD 27 MGD Figure 25: Monthly Minimum Dissolved Oxygen from Streeter-Phelps Analysis of San Joaquin Time O" Distance DO min. DO min. DO min. River and WQCF Discharge Month (d)(1) (miles) (mg/L) (mg/L) A(mg/L)(�) (mg/L) A(mg/L)(2) Jan 2.9 40.7 8.95 8.93 -0.02 8.91 -0.04 Comparison to Water Quality Objectives: The DO objective in the San Joaquin River Feb 0.5 5.9 8.78 8.76 -0.02 8.74 -0.04 between Turner Cut and Stockton during September through November is 6 mg/L;otherwise,the objective is 5 mg/L for the river within the boundaries of the Delta. For both the DWSC DO and Mar 2.4 30.8 8.09 8.07 -0.02 8.05 0.04 minimum DO downstream from the WQCF discharge,the proposed project does not effect DO Apr 4.5 62.5 7.44 7.42 -0.02 7.40 0.04 concentrations by more than 0.2 mg/L. May 4.6 63.8 7.04 7.02 -0.02 7.00 0.04 Evaluation: Because the load of biologically oxidizable material carried by the San Joaquin Jun 4.0 43.0 7.22 7.21 -0.01 7.19 0.03 River at R-1 far overshadows the load from the WQCF at project build-out,the incremental Jul 3.3 33.5 6.90 6..88 -0.02 6.87 0.03 change in DO due to the project is minor both in the river downstream of the WQCF or in the Aug 1.8 17.9 6.71 6.70 -0.01 6.69 -0.02 DWSC. As part of the phased approach to the adopted Total Daily Maximum Load(TMDL)for Sep 2.3 23.3 7.30 7.28 -0.02 7.27 0.03 DO in the DWSC(CVRWQCB,2005),studies are currently being performed to allow Oct 1.7 21.5 7 09 7.08 -0.01 7.07 -0.02 calculation of waste load and load allocations to achieve the DO targets in the DWSC. Load from the WQCF has little effect on the DWSC DO concentrations and WLAs scheduled for the Nov 0.0 0.0 7.80 7.79 0.01 7.78 0.02 December 2009 revisitation of the TMDL should not be required for the WQCF discharge. Dec 0.0 0.0 8.68 8.66 -0.02 8.64 -0.04 Because of the small impact on DO,the WQCF discharge should fall into the margin of safety or (1)Critical flow time corresponding to the 9.87 MGD case.The float time for the 17.5 MGD and 27 MGD cases is nearly identical. (2)Difference between DO-for case and DO, for 9.87 MGD case. City of Manteca Antidegradation Analysis 77 June 2007 City of Manteca Antidegradation Analysis 78 June 2007