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WASTE DISCHARGE REQUIREME RDER NO R5-2012-0106 • 3_ GLENN SPRINGS HOLDING COMPAIQY, FORMER OCCIDENTAL CHEMICAL COMPANY, GROUNDWATER REMEDIATION PROJECT, LATHROP FACILITY SAN JOAQUIN COUNTY 13. The Discharger also proposes to operate four (4) injection wells screened above the Corcoran Clay, after installing two new wells and converting two existing extraction wells to injection wells. Injection into wells INJ-11, INJ-12, INJ-13/EW-03 and ]NJ- 14/EW-04 will accelerate cleanup of sulfolane, DBCP, and EDB in groundwater beneath the Site. Additional injection wells may be added if needed under subsequent phases of work with written approval from the Central Valley Water Board. 14. The Discharger also proposes to extract groundwater from J.R. Simplot's existing backup water supply well and operate a wellhead treatment system to remove sulfolane from extracted groundwater. At times, treated backup supply well water will be injected above the Corcoran Clay to enhance sulfolane remediation. At other times, treated water will be supplied to J.R. Simplot for their use as process water or for irrigation purposes. The average flowrate from the backup supply well is expected to be approximately 250 gallons per minute (gpm) and the maximum flowrate would be 700 gpm. 15. The Discharger has proposed to increase the total extraction rate, including extraction from J.R. Simplot's backup water supply well, to an average flow of 750 to 1,000 gpm; with a potential maximum flow rate of 2,000 gpm. The disposal of the treated groundwater under Order No. 83-039 was below the Corcoran clay, The new disposal will have up to 750 gpm disposed to lW-1 and IW-2 below the Corcoran Clay and up to 1,250 gpm to the proposed injection wells screened above the Corcoran Clay. The current treatment system has a capacity of 750 gpm. The discharger will be installing another remediation system to treat additional water collected from J.R Simplot's backup supply well. The.extraction and injection flow rates will not exceed the demonstrated treatment system capacities 16. The groundwater remedial system has operated since 1982. In recent years, in addition to routine operation and maintenance of the system, the Discharger has reconditioned the treatment system and optimized pumping from the extraction well network; installed additional extraction wells EW-8A, EW-8B, and EW-9; investigated a suspected source area of sulfolane with high sulfolane soil concentrations; added additional groundwater monitoring wells PW27-40, PW28-40, and PW29-40; and confirmed stable or shrinking pollutant plumes. The Discharger also modified the bioreactor/GAC treatment flow configuration from up-flow parallel to down-flow series, increased the dissolved oxygen concentration added prior to GAC treatment by using an oxygen delivery system in order to improve the aerobic biodegradation of sulfolane. With these modifications, each GAC vessel can now be separately adjusted to improve aerobic biological treatment of sulfolane in the lead vessel and sorption of EDB and DBCP in the lag vessel. 17. Groundwater extraction and treatment has reduced the concentrations and extent of sulfolane, DBCP and EDB. As of August 16, 2012, concentrations of sulfolane, DBCP and EDB in groundwater in the combined influent to the treatment system were 850, 1 .2, and 0.0045 micrograms per liter (pg/L), respectively. To date, the system has