ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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Evaluation of Consistency with Antidegradation • Based on the above,the requested increase in permitted capacity is consistent with Federal and State antidegradation policies in that the lowering of water quality for several Policy pollutants is necessary to accommodate important economic or social development,will not unreasonably affect beneficial uses,will not cause further exceedances of applicable The guidelines set by the State Water Board for the antidegradation analysis(APU 90-004) water quality objectives,and is consistent with the maximum benefit to the people of the provide direction on evaluating the WQCF's proposed discharge increase into the San Joaquin State. River by focusing on whether and the degree that water quality is lowered and by considering whether or not the assumed water quality change is consistent with the maximum benefit to the • Based on the above,the requested increase in permitted capacity is consistent with the people of the State. In developing the antidegradation analysis,the San Joaquin River beneficial Porter-Cologne Act in that the resulting water quality will constitute the highest water uses and relevant water quality objectives and commonly used criteria were considered,as well quality that is reasonable,considering all demands placed on the waters,economic and as the environmental and socio-economic costs of wastewater treatment alternatives that would social considerations,and other public interest factors. maintain existing water quality in an effort to avoid any potential environmental impacts of the proposed project. CONSISTENCY WITH ANTIDEGRADATION POLICIES The proposed project,a 17.13 MGD(ADWF)increase in WQCF discharge capacity with accompanying nitrification-denitrification,tertiary filtration,and UV disinfection treatment upgrades to treat the increased flow,is determined to comprise best practicable treatment or control and is consistent with Federal and State antidegradation policies for the following reasons: • The increase in permitted discharge capacity is necessary to accommodate important economic and social development in the City and surrounding communities,and is consistent with the City's General Plan. Failure to approve the increase,or alternatively requiring the City to implement control measures that would maintain existing water quality and mass emissions in the San Joaquin River,would have significant adverse economic and social impacts on the City and surrounding communities and their citizens and businesses. • The increase will not adversely affect existing or probable beneficial uses of the San Joaquin River,nor will it cause water quality to fall below applicable water quality objectives. • The increase,while causing slight increases in downstream water quality concentrations for some constituents(ammonia(October through May),dissolved arsenic,dissolved copper,total cyanide,MBAS,nitrate,nitrite,total mercury,and EC(September through March)),will produce slight decreases in downstream concentrations for others(TSS, total aluminum,dissolved iron,and dissolved manganese). The proposed increase in discharge capacity is also projected to cause minor increases in downstream water quality concentrations for BOD and EC(April through August),as well as a moderate increase for ammonia(June through September). Total aluminum currently exceeds its water quality objective in the San Joaquin River upstream of the WQCF outfall. • The benefits of maintaining existing water quality and mass emissions for the constituents analyzed are not commensurate with the costs of additional treatment. The small decrease in quality with respect to the constituents considered in the analysis is unlikely to affect beneficial uses of the San Joaquin River. City of Manteca Antidegradation Analysis 121 June 2007 City of Manteca Antidegradation Analysis 122 June 2007