ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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These General Permits require(1) submittal to the Central Valley RWQCB of a Notice of Intent(NOI)to discharge, and(2)preparation of a stormwater pollution prevention plan(SWPPP)that identifies and describes the best management practices (BMPs)to be implemented at the site to minimize pollution from stormwater runoff. The Central Valley RWQCB may also issue site-specific WDRs, or waivers to WDRs, for certain waste discharges to land or waters of the state. In particular, Central Valley RWQCB Resolution R5-2003-0008 identifies activities subject to waivers of WDRs and/or WDRs for a variety of activities, including minor dredging activities and construction dewatering activities that discharge to land. For example,the Central Valley RWQCB's general NPDES permit for construction dewatering activity(Order 5-00-175) authorizes direct discharges to surface waters up to 250,000 gallons per day for no more than a 4-month period each year. Construction activities subject to the general construction activity permit include clearing, grading, stockpiling, and excavation. Dischargers are required to eliminate or reduce nonstormwater discharges to storm sewer systems and other waters. The permit also requires dischargers to consider the use of permanent post-construction BMPs that would remain in service to protect water quality throughout the life of the project. All NPDES permits also have inspection,monitoring, and reporting requirements. In response to a court decision,the Central Valley RWQCB implemented mandatory water quality sampling requirements in Resolution 2001-046 for visible and nonvisible contaminants in discharges from construction activities. Water quality sampling is now required if the activity could result in the discharge of turbidity or sediment to a water body that is listed as impaired under Section 303(d)because of sediment or siltation, or if a release of a nonvisible contaminant occurs. Where such pollutants are known or should be known to be present and have the potential to contact runoff, sampling and analysis is required.NPDES permits require the implementation of design and operational BMPs to reduce the level of contaminant runoff. Types of BMPs include source controls, treatment controls, and site planning measures. Discharges subject to the SWRCB's NPDES general permit for construction activity must develop and implement a SWPPP. The SWPPP includes a site map and description of construction activities and identifies the BMPs that would be employed to prevent soil erosion and discharge of other construction-related pollutants(e.g.,petroleum products, solvents,paints,cement)that could contaminate nearby water resources. A monitoring program is generally required to ensure that BMPs are implemented according to the SWPPP and are effective at controlling discharges of stormwater-related pollutants. Manteca WQCF NPDES Permit The Manteca WQCF presently operates and discharges treated effluent to the San Joaquin River under the requirements of a NPDES permit issued by the Central Valley RWQCB in Order No. R5-2004-0028 and as amended by Order No. R5-2005-0110. The permit includes three sets of effluent limitations for discharge to the San Joaquin River based on the design treatment capacity of the WQCF as it undergoes its scheduled improvements. The permit contains effluent limitations for design treatment capacities of 6.95, 8.11, and 9.87 mgd. Table 4.9-9 presents the effluent limits for the 9.87 mgd design treatment capacity contained in the City's NPDES permit. A copy of the permit is included in Appendix E. Table 4.9-9 Adopted Effluent Limits for City's WQCF Discharge to the San Joaquin River at a 9.87 MGD ADWF Design Treatment Capacity Constituent Units Monthly Average Weekly Average 1-Hour Average Daily Maximum BOD' mg/l 102 202 — 302 TSS mg/l 102 20' — 302 Total Coliform MPN/100 mL — 2.2(3) — 23/2404 Turbidity NTU 2(5) 5/106 Settleable Solids ml/1 0.1 0.2 DEIR EDAW City of Manteca 4.9-21 Hydrology and Water Quality