FIELD DOCUMENTS AND WORK PLANS 1992-1999

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INFORMATION SHEET MARLEY COOLING TOWER COMPANY STOCKTON, SAN JOAQUIN COUNTY Facility Description and Discharges The Marley Cooling Tower Company (MCTC) owns a cooling tower fabrication plant in the east Stockton area. As part of the fabrication process, MCTC operated a wood treatment facility at the site until January 1991 at which time wood treatment was ceased. The primary chemicals used in the wood treatment process were copper and chromium. Arsenic was also used in the wood treatment solutions until 1982. The site is divided into two areas, the North and South Yards. All wood treating activities were performed and all treated products were stored in the North Yard. Rainfall contacting the North Yard becomes contaminated with wood treatment chemicals. MCTC has implemented controls to reduce rainfall contamination and contain all runoff in the North Yard. Previously, all contaminated stormwater from the North Yard was discharged to an on-site holding pond for evaporation and infiltration. Contaminated stormwater is now conveyed to an on-site treatment plant before discharge to the Stockton Diverting Canal . The South Yard is used for fabrication and storage of not treated cooling tower components. Stormwater from the South Yard is discharged directly to the local drainage ditch system. MCTC conducted cleanup of residual contamination in the South Yard. Runoff from the South Yard is not being regulated. Past operational practices by MCTC have resulted in soil and ground water contamination by wood treatment chemicals. Soils beneath the wood treatment retort contain elevated levels of copper, chromium, and arsenic. Underlying ground water has been contaminated with chromium and copper. Ground water contamination exceeding the state drinking water standard for total chromium of 50 ug/l extends approximately 1000 feet off-site to the southwest. First ground water is approximately 80 feet below ground surface. The depth of ground water contamination extends to approximately 200 feet. In October 1987, MCTC initiated interim ground water remediation. This interim remedial action has been operating under Order No. 91-035 (NDPES No. CA00817887) . MCTC is presently permitted to discharge up to 0.59 mgd of treated stormwater and ground water to the Stockton Diverting Canal , tributary to the Calaveras River. The Stockton Diverting Canal is an engineered drainage way connecting Upper Mormon Slough to the Calaveras River near the Southern Pacific Railroad crossing. Upper Mormon Slough is actually the South Fork of the Calaveras