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INFORMATION SHEET J. R SIMPLOT COMPANY STORMWATER SURFACE IMPOUNDMENT AND CLASS Il SURFACE IMPOUNDMENTS SAN JOAQUIN COUNTY J. R Simplot Company (Simplot) manufactures and formulates fertilizer at this facility in Lathrop, California. Simplot discharges wastewater to both unlined and lined surface impoundments. The following is a description of Simplot's wastewater system and rationale for some of the requirements set forth in these waste discharge requirements. Facility Description Simplot's Lathrop facility is south of the city of Stockton in south central San Joaquin County, Section ' 35, TIS, R6E MDB&M on approximately 341 acres. This facility was previously owned by Occidental Chemical Company. Occidental manufactured and formulated both fertilizers and pesticides at this facility. In the late 1970s, prior to transfer of the facility to Simplot, ground water at this site was found to.be contaminated with some organic pesticides (primarily dibromochloropropane and ethylene dibromide). A Stipulated Agreement for inyestignion and cleanup of the site was approved by the Court in the early 1980s as described in findings Nos. 5 and 6 of these requirements. Essentially, Occidental is responsible for site cleanup while Simplot is responsible fai managing wastes discharged subsequent to the transfer of the fac}ity. Simplot no longer formulates pesticides at the Lathrop facility. Simplot discharges up to 0.05 million gallons per day (mgd) of process waters and washdown water to lined ponds. These lined ponds consist of one 3.5-double7lined (one Hypalon and'one PVC) pond, one 2.8-acre double Hypalon-lined pond, and one 3.2-a6re, double hypalon-lined pond. Simplot discharges an average of 0.3 mgd of stormwater runoff from the fertilizer process area-and zeolite softener backwash water to these lined ponds also. This wastewater generally has high concentrations of total dissolved solids (TDS), primarily ammonium sulfate and calcium oxide. Thiswater is recycled for use in the manufacture of fertilizers and is classified as 'designated'using the criteria set forth m Title 27. Simplot w also discharges an average of 0.089 mgd of stormwater runoff, cooling tower blowdown, reverse osmosis and boiler blowdown, and`wastewater from a small package sewage treatment plant to a 7.8-acre unlined pond. Tis wastewater is exempt from the requirements of Title 27 as described in finding No. 13, but is also regulated by these waste discharge requirements. Simplot's existing ground water monitoring at this site indicates that water quality may have been impacted from discharges from a former asphalt-lined pond (now double-lined) containing elevated levels of TDS and sulfates. (Shallow ground water in the area has elevated concentrations of TDS above the primary drinking water standard of 500 mg/l.) Since 1994, Simplot has retrofitted the asphalt-lined pond and both single-lined hypalon ponds under a schedule contained in Order No. 94-189, which specifies waste discharge requirements for the impoundments. The last single-lined pond was retrofitted during the summer or 1996. The new liner systems conform to the requirements of Title 27, and are part of the Corrective Action for this facility. 1_