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r M <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION <br /> RESOLUTION NO. R5-2004- <br /> AMENDING CEASE AND DESIST ORDER NO. R5-2004-0029 <br /> NPDES NO. CA0081558 <br /> CITY OF MANTECA <br /> WASTEWATER QUALITY CONTROL FACILITY <br /> SAN JOAQUIN COUNTY �T <br /> The California Regional Water Quality Control Board, Central Valley Region, (hereafter Regional lr <br /> Board)finds: <br /> 1. On 19 March 2004,the Regional Board adopted Waste Discharge Requirements Order No. <br /> R5-2004-0028,NPDES No. CA0081558,prescribing waste discharge requirements for the City <br /> of Manteca, City of Lathrop, and Dutra Farms at the Manteca Wastewater Quality Control 1 <br /> Facility(WQCF) in San Joaquin County. For the purposes of this Resolution,the City of <br /> Manteca is hereafter referred to as "Discharger." <br /> The Discharger owns and operates a wastewater collection,treatment, and disposal system, and A <br /> provides sewerage service to the City of Manteca and the City of Lathrop. Land disposal of <br /> effluent is maximized by discharging effluent at agronomic rates seasonally to existing City- <br /> owned property and additional leased property. Excess flow of treated municipal wastewater is <br /> discharged to the San Joaquin River. r� <br /> 2. The Regional Board found that the discharge from the WQCF is not able to consistently 1 <br /> comply with final effluent limitations for aluminum, ammonia, arsenic, copper, cyanide, iron, <br /> manganese, MBAS,nitrate, nitrite,temperature, and electrical conductivity,nor receiving water <br /> limitations for temperature or oil and grease. Therefore,pursuant to California Water Code T <br /> Section 13301,the Regional Board also issued Cease and Desist Order No. R5-2004-0029 on 1 <br /> 19 March 2004 with requirements and time schedules to bring the discharge into full <br /> compliance with the final effluent and receiving water limitations. <br /> 3. The WQCF has historically operated in a non-nitrifying or partial nitrifying mode, which V <br /> typically produced an effluent with low nitrate concentrations. However,the effluent exhibited <br /> elevated levels of ammonia, often at concentrations toxic to aquatic life. When the waste <br /> discharge requirements were adopted,the WQCF was still operating in this mode, and the <br /> Discharger received interim effluent limits based on the plant performance at that time. Since T <br /> 1 April 2004,the treatment process was converted to full nitrification mode. As a result, <br /> effluent ammonia concentrations have improved while nitrate concentrations have significantly <br /> increased. The Discharger is now unable to comply with the established interim effluent nitrate <br /> limitation specified in Order No. R5-2004-0029. <br />