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ITEM: 7 SUBJECT: SPX Corporation, Marley Cooling Tower Company, Groundwater Extraction and Treatment System. San Joaquin County BOARD ACTION: Consideration of NPDES Permit Renewal BACKGROLND: The Discharger previously operated a wood preservation process at the site using solutions containing copper, chromium and arsenic. Wood preserving was discontinued at this facility in January 1991, however past operational practices have resulted in contamination of soils and groundwater underlying the site. The on-going groundwater remedial action at the site includes the extraction, treatment, and discharge of treated groundwater. Groundwater is extracted from wells on and off- site, and conveyed to the groundwater treatment system. The groundwater treatment system at the plant includes an electrochemical reduction and precipitation unit operating in parallel to an ion exchange treatment system. The groundwater treatment system is designed to treat a maximum daily flow up to 0.94 mgd. Treated groundwater is subsequently discharged to the Stockton Diverting Canal (SDC), a tributary to the Calaveras River. On 16/17 September 2002, a system malfunction resulted in a discharge of high pH water and a significant fish-kill in the SDC. ISSUES: Designation of Beneficial Uses,New TDS Effluent Limit: The beneficial uses of the SDC are not identified in the Basin Plan. Use of the tributary language in the Basin Plan and the application of State Board Resolution 88-63, Sources of Drinking Water Policy, resulted in the designation of municipal and domestic supply(MUN) and agricultural supply(AGR) beneficial uses to the SDC in this proposed Order. Order No. 93-221 includes an existing monthly average limitation for total dissolved solids (TDS) of 1000 mg/L(ppm). Because M`U is identified in this proposed Order as a beneficial use of the SDC, and because current information indicates there are periods of limited or no flow in the SDC, this proposed Order includes a new final monthly average effluent limitation for TDS of 500 mg/L protective of MCN (Secondary MCL). • Consideration of AGR Beneficial Use: The new final effluent limitation for TDS may not be fully protective of the SDC for unlimited AGR use under all conditions. Provisions of this Order allow the Discharger time to; study the hydrologic characteristics of the SDC, consider the Basin Plan amendment process and de-designation of beneficial uses, study site specific conditions that affect the AGR water quality criteria concentration, and/or, evaluate alternative treatment or disposal options.