ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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effluent ammonia levels on DO levels in the San Joaquin River is addressed in the Far-Field Ammonia as Nitrogen(Oct.-May) Analysis and Results section of this report in a discussion of far-field DO impacts. Additionally, it should be noted that ammonia levels will decline over time and distance downstream of R-3 as 6 ammonia is utilized by phytoplankton and other primary producers. J 5 SJR Flows E 4 Table 16: Estimated Impact of Ammonia(as Nitrogen)from WQCF Discharge during June through �600 cfs September in the San Joaquin River at WQCF R-3 3 �1250 cfs c11 2 -Acute WQO Ammonia as Nitrogen(June-Sept.) San Joaquin River Manteca WQCF Effluent c 1 R-1 50"%concen.(mg/L)* 0.13 Flowrate(cfs) Flowrate(MGD ADWF) v Projected effluent concen.(mg/L) 1 1.5 600 1250 9.87 17.5 27 0 9.87 17.5 27 Est.mass loading(lbs/day) 420 876 123 219 338 WQCF Effluent Flow Rate(MGD) Est.downstream R-3 river concentration(mg/L)at 600 cfs 0.16 0.19 0.22 Est.downstream R-3 river concentration(mg/L)at 1250 cfs 0.15 0.16 0.17 `50"percentile statistic calculated using the following data set: Figure 11: Projected Change in San Joaquin River Ammonia(as Nitrogen)Concentration at Data Period:June 2002-September 2002,September 2004;Sample Size,n=5;Percent Detected Data=80% WQCF R-3 during October through May with increasing WQCF Effluent Flowrate Comparison to Water Ouality Objective: The U.S.EPA ambient water quality criteria that are Table 17: Estimated Impact of Ammonia(as Nitrogen)from WQCF Discharge during October applied to ammonia concentrations in the San Joaquin River are pH and temperature dependent. through May in the San Joaquin River at WQCF R-3 The acute and chronic criteria for ammonia as promulgated by U.S.EPA 1999 Update of Ammonia as Nitrogen(Oct.-May) San Joaquin River Manteca WQCF Effluent Ambient Water Quality Criteria for Ammonia are used by the Regional Water Board to interpret " Flowrate(cis) Flowrate(MGD ADWF) the Basin Plan's narrative toxicity objective. Using pH and temperature values previously used R-1 50 %concen.(mg/L)* 0.08 by the Regional Water Board in WDR Order No.R5-2004-0028,a chronic criterion of 0.62 Projected effluent concen.(mg/L) 1.5 600 1250 9.87 17.5 27 mg/L ammonia(as nitrogen)can be calculated and applied to the San Joaquin River during June Est.mass loading(lbs/day) 259 539 123 219 338 through September based on an ambient pH of 8.4 standard units and an ambient temperature of Est.downstream R-3 river concentration(mg/L)at 600 cfs 0.12 0.14 0.17 26°C. Similarly,an acute criterion of 5.62 mg/L ammonia(as nitrogen)can be calculated and Est.downstream R-3 river concentration(mg/L)at 1250 cfs 0.10 0.11 0.13 applied to the San Joaquin River during October through May based on an ambient pH of 8.0 '50'"percentile statistic calculated using the following data set: standard units. The acute ammonia criterion is not temperature dependent. Estimated Data Period:January 2002-May 2002,October 2002-May 2004;Sample Size,n=11;Percent Detected Data=72.7% concentrations of ammonia(as nitrogen)in the San Joaquin River under critical and dry/below normal flow conditions show a more pronounced increase relative to the chronic EPA criterion during June through September,than the slight increase relative to the acute EPA criterion during October through May,with an increase in WQCF effluent discharge from 9.87 MGD (ADWF)to 27 MGD(ADWF). In an analysis of compliance with chronic and acute seasonal objectives(Figure 10 and Figure 11),projected median ammonia(as nitrogen)concentrations in the San Joaquin River remain below the more stringent chronic ammonia objective(0.62 mg/L) calculated for the river on a year round basis. Evaluation: A high level of nitrogen removal will be accomplished through the activated sludge nitrification-denitrification process implemented as one of several treatment process improvements associated with the WQCF upgrade. Most importantly,the present analysis shows that projected,median ammonia(as nitrogen)concentrations in the San Joaquin River are below the more stringent chronic criterion of 0.62 mg/L during the June through September time period,and substantially lower than the acute criterion of 5.62 mg/L during the October through May time period. The consumptive oxygen demands of ammonia nitrification are most strongly expressed downstream of the City's wastewater outfall,and therefore the impact of WQCF City of Manteca Antidegradation Analysis 45 June 2007 City of Manteca Antidegradation Analysis 46 June 2007