ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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be harmful to fish. By decreasing effluent ammonia levels,nitrification-denitrification increases dissolved oxygen concentrations in receiving waters to nontoxic levels. The land outfall for river discharge consists of approximately 14,000 feet of 36-inch diameter pipe,which is routed from the chlorine contact tank along the westerly perimeter of the WQCF property. The outfall pipeline has a capacity range of 7.2 to 17.7 mgd under gravity flow conditions, depending on the water-surface elevations in the San Joaquin River. Effluent from the plant is routed through the pipeline to a side-bank outfall structure at the San Joaquin River. The outfall structure consists of a concrete junction manhole for maintenance access, a headwall structure with flap gate to prevent reverse flow, and a concrete spillway to the river edge. Riprap is provided at the bottom of the spillway for erosion protection as well as to dissipate energy during peak flows. The spillway is enclosed on three sides by concrete walls to prevent any spill and to direct flow to the river. The proposed project would expand this structure to accommodate a second parallel outfall pipe. To comply with certain temperature requirements,treated effluent discharged to the San Joaquin River is only allowed when the river has a certain downstream flow condition. To address this operational constraint, Schedule D off-line storage improvements for the treated effluent will allow the WQCF to store effluent during certain river flow conditions. River flow data from an existing real-time in-stream flow meter, located at the Mossdale Bridge, monitors the flow within the river. Treated effluent scheduled for land application bypasses the chlorine contact tank and is routed to a 10-acre balancing pond(designated as a secondary effluent storage pond). Effluent is released from the pond for flood irrigation of agricultural fields frequently during the growing season. Depending on the location of the agricultural field,unchlorinated secondary effluent either flows by gravity from the balancing pond or is pumped from the effluent irrigation pumping station. The Central Valley Regional Water Quality Control Board has issued a discharge permit based on application of treated effluent to land at"hydraulic-agronomic"rates,with excess effluent permitted to flow to the San Joaquin River. The regional board specifically stated that flows to agricultural lands should be maximized to limit discharge to surface waters. The permit does not,however,restrict the number of days the WQCF can discharge to the river. As a goal, it is assumed that 6 months of the year(180 days)the plant will discharge to the river,and the rest of the year the effluent can be applied to land. Septage Receiving A number of haulers deliver septage waste to the WQCF daily. The 1,000-2,000-gallon tanker trucks discharge septage directly into the wet well of the influent pump station. EXISTING SOLIDS STREAM TREATMENT SYSTEM Solids stream processing areas include grit, screenings,and scum treatment, solids thickening, solids digestion, dewatering, storage, and disposal. Screenings, Grit, and Scum Screenings (i.e.,large debris such as rags)are mechanically removed from the bar screens, dewatered, and disposed. Grit collected from the aerated grit tanks is conveyed to separators and a classifier where it is dewatered and disposed. Scum generated from the primary treatment process (i.e., floating debris and foam)is removed with skimmers from the primary sedimentation basins and pumped to the anaerobic digesters. Scum generated from the secondary treatment process is collected from the secondary clarifiers and pumped to the anaerobic digesters. EDAW Manteca WQCF and Collection System Master Plans EIR Project Description 3-14 City of Manteca