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STAFF REPORT <br /> SPX CORPORATION <br /> MARLEY COOLING TOWER COMPANY <br /> GROUNDWATER EXTRACTION AND TREATMENT SYSTEM <br /> SAN JOAQUIN COUNTY <br /> A renewed NPDES Permit is being considered for adoption for the SPX Corporation,Marley <br /> Cooling Tower Company, Groundwater Extraction and Treatment System. <br /> BACKGROUND <br /> The Marley Cooling Tower Company(MCTC), a wholly owned subsidiary of SPX Corporation <br /> (hereafter Discharger) owns and operates a groundwater extraction and treatment system in the East <br /> Stockton Area of San Joaquin County. The Discharger previously operated a cooling tower <br /> fabrication plant at the site which included a wood preservation process using solutions containing <br /> copper, chromium and arsenic. Wood preserving was discontinued at this facility in January 1991, <br /> however past operational practices resulted in contamination of soils and groundwater underlying the <br /> site. Pursuant to a settlement agreement between the Department of Toxic Substances Control <br /> (DTSC)), the Discharger, and the Regional Board, the on-going groundwater remedial action at the <br /> site includes the extraction, treatment, and discharge of treated groundwater to the Stockton <br /> Diverting Canal, a tributary to the Calaveras River. The discharge was previously regulated by <br /> Waste Discharge Requirements Order No. 93-221, NPDES Permit No. CA0081787. Under this <br /> Order, the Discharger was permitted to discharge a maximum of 0.94 million gallons per day(mgd) <br /> of treated water to the Stockton Diverting Canal. <br /> ISSUES <br /> Designation of Beneficial Uses, New Total Dissolved Solids Effluent Limitation <br /> The beneficial uses of the SDC are not identified in the Basin Plan. Use of the tributan language in <br /> the Basin Plan and the application of State Board Resolution 88-63, Sources of Drinking Water <br /> Policy, resulted in the designation of municipal and domestic supply(MUN) and agricultural supply <br /> (AGR)beneficial uses to the SDC in this proposed Order. <br /> Order No. 93-221 includes an existing monthly average limitation for total dissolved solids (TDS) of <br /> 1000 mgfL(ppm). Because MUN is identified in this proposed Order as a beneficial use of the SDC, <br /> and because current information indicates there are periods of limited or no flow in the SDC, this <br /> proposed Order includes a new final monthly average effluent limitation for TDS of 500 mg/L <br /> protective of MUN (Secondary MCL). Currently, monthly average concentrations of TDS in the final <br /> effluent exceed the new effluent limitation established in this Order. The Regional Board, however, <br /> does not have sufficient information to determine if there is reasonable potential to violate the <br /> narrative water quality objective. Preliminary data provided by the Discharger indicate the SDC may <br /> provide some dilution and have some limited assimilative capacity for TDS, however, the receiving <br /> water characteristics have not been fully evaluated with respect to TDS. This proposed Order <br /> provides time for the Discharger, if they elect, to further study the characteristics and potential <br /> assimilative capacity of the SDC, consider the appropriateness of the MUN and/or AGR beneficial <br /> use designation of the SDC, and/or consider disposal and treatment alternatives. As this is a <br />