SITE INFORMATION AND CORRESPONDENCE_FILE 1

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WASTE DISCHARGE REQUIREMENTS OCCIDENTAL CHEMICAL AGRICULTURAL PRODUCTS, INC LATHROP, SAN JOAQUIN COUNTY -2- 9. OCAP will discharge treated ground water, plus approximately 263,000 gallons per year (995,000 liters per year) of demineralizer backwash water, at a maximum rate of approximately 750 gallons per minute (2,840 liters per minute) through injection wells into an aquifer. 10. Ground water underlying and in the vicinity of the Lathrop property is contaminated with sulfates, dibromochloropropane (DBCP), sulfolane, ethylene dibromide (EDB), lindane and other isomers of BHC, dimethoate, and disyston. 11. The ground water remedial system consists of containment and extraction of the ground water through five strategically placed wells, treatment of the extracted ground water by carbon adsorption, and disposal of the treated water by injection through two deep wells into a confined aquifer isolated from useable ground waters. 12. The demineralizer backwash water is produced from a zeolite water softener owned and operated by Simplot. This wastewater is the only waste stream accepted by OCAP from Simplot for disposal by deep well injection. 13. The injection aquifer has a total dissolved solids concentration of approxi- mately 3000 mg/1 with a chloride concentration of 1000 mg/1 or greater, making the aquifer unuseable for agricultural or domestic uses. 14. The injection aquifer is overlain by a thick confining layer of relatively impermeable blue clay (commonly referred to as the Corcoran clay layer). The clay layer is found at a depth of 230-280 feet (70 to 85 meters) to 300-340 feet (92 to 104 meters) and averages 50 to 80 _feet (15.2 to 24.4 meters) thick. The minimum thickness of the clay Tayer_is about 30 feet. 15. Pump and injection tests show the injection aquifer to be confined and isolated by the Corcoran clay layer from overlying useable ground water within at least a radius of one mile (1.6 km) from the point of injection. The one mile radius (1.6 km) is the potential "zone of endangering influence" calculated for a 20 year time period based on the hydrologic data obtained from the pump and injection tests. 16. The treated ground water and demineralizer backwash water will be injected between the depths of 300 (92 m) and 500 feet (150 m) at an estimated pres- sure of 17 psi (1.2 atm) at startup to nearly 52 psi (3.5 atm) after about 10 years of injection. The maximum injection pressure is about 40 percent of the hydrofracture pressure (129 psi). All pressures are measured as gauge pressures. 17. The injection waters are not classified as hazardous. The quality of the waters will meet established drinking water standards or state action levels for toxic contaminants. If toxic contaminants with no established standards are detected in the injection waters, the state and EPA will establish standards or criteria based on current toxicological information.