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CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION <br /> ORDER NO. 97-115 (REVISED) <br /> NPDES NO. CA0081558 <br /> WASTE DISCHARGE REQUIREMENTS <br /> FOR <br /> CITY OF MANTECA AND CITY OF LATHROP <br /> WASTEWATER QUALITY CONTROL FACILITY <br /> SAN JOAQUIN COUNTY <br /> The California Regional Water Quality Control Board, Central Valley Region, (hereafter Board) finds <br /> that: <br /> 1. The City of Manteca and the City of Lathrop (hereafter Discharger) submitted a Report of Waste <br /> Discharge, dated 28 December 1995, and applied for a permit renewal to discharge waste under <br /> the National Pollutant Discharge Elimination System (NPDES). <br /> The City of Manteca's wastewater treatment plant accepts wastewater flows from certain areas of <br /> the City of Lathrop, therefore the City of Lathrop is also named in this permit and it is <br /> responsible for its wastewater collection system. The City of Manteca is solely responsible for <br /> the wastewater treatment facility. <br /> On 9 July 1999, the City of Manteca requested modification of their permit to allow a change of <br /> their effluent toxicity requirements through utilization of a mixing zone in the receiving water. <br /> Additional information on this request was submitted on 22 July 1999, 23 November 1999, <br /> 3 December 1999 11 January 2000 and 14 January 2000. <br /> Revisions to this permit are limited to acute effluent toxicity requirements, mitigations as <br /> described in the findings (which includes establishment of a mixing zone), and effluent <br /> monitoring in the monitoring and reporting program. <br /> 2. The Board, on 29 May 1991, adopted Waste Discharge Requirements Order No. 91-110 (NPDES <br /> No. CA 0081558)which prescribed requirements for a discharge of 5.75 million gallons per day <br /> (mgd) of treated combined domestic and industrial wastewater to land and partially to surface <br /> water. Land disposal of effluent is maximized by discharging effluent at agronomic rates <br /> seasonally to existing City-owned irrigation fields, and additional leased property as shown on <br /> Attachment "A", a part of this Order. Excess flows are discharged to the San Joaquin River, a <br /> water of the United States, at a point in Section 4, T2S, R6E, MDB&M, as shown on Attachment <br /> "B", a part of this Order. <br /> 3. Order 97-115, adopted by the Board on 20 July 1997, renewed prescribed requirements for the <br /> City's discharge and increased their effluent flow from 5.75 mgd to 8.11 mgd after the <br /> completion of the proposed wastewater treatment plant expansion. <br /> 4. Order No. 97-115 prescribed stricter effluent toxicity limitations than the previous permit. <br /> Specifically, the acute toxicity bioassay parameters were revised to require compliance with the <br /> latest testing procedures contained in EPA/600/4-90/027F. Furthermore, the bioassay test <br /> species were restricted to fathead minnows and golden shiners. The new EPA procedure requires <br />