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WASTE DISCHARGE REQUIREMEN410RDER NC R5-2012-0106 -4- GLENN SPRINGS HOLDING COMPANY, FORMER OCCIDENTAL CHEMICAL COMPANY, GROUNDWATER REMEDIATION PROJECT, LATHROP FACILITY SAN JOAQUIN COUNTY removed approximately 12,300 pounds (lbs) of sulfolane, 4,000 lbs of DBCP, and 220 lbs of EDB. 18. EDB and DBCP have not been detected in the injection zone monitoring wells below the Corcoran Clay since at least 1998. The best currently approved analytical methods for DBCP have detection levels of 0.001 erg/L and practical quantitation levels of 0.01 pg/L. The practical. quantitation level is above the effluent limitation for DBCP found in this Order. Compliance with the effluent limitation is demonstrated by measuring no detectable concentrations of DBCP when using the method(s) listed on MRP R5-2012- 0106 and achieving the specified method detection limit. If new methods are approved that improve on the detection level and practical quantitation level, the MRP will be revised. 19. Based on the most recent data collected in August and September 2011, sulfolane is present in injection zone.monitoring wells PW09-338 and PW12-315 at 65 pg/L and 170 pg/L, respectively. There was no treatment goal for sulfolane until 1992, so concentrations of sulfolane in the injection zone reflect the injection of untreated sulfolane from 1982 to 1992 and concentrations in the injectant that were below the previous discharge limit of 57 pg/L established after 1992. 20. Total dissolved solids (TDS) in the.injection zone monitoring wells averages 2,479 milligrams per liter (mg/L) with a maximum concentration of 4,860 mg/L. The highest TDS concentrations were measured west of the Site, in PW20-500, where groundwater quality-is most affected by saline water from the San Francisco Bay Delta. Chloride accounts for the majority of TDS in PW20-500. TDS concentrations in treatment system effluent average 2,369 mg/L with a maximum concentration of 3,150 mg/L. Sulfate accounts for the majority of TDS in the treatment system effluent. TDS concentrations in the treatment system effluent are expected to stay within the same range after the proposed additional extraction wells begin operation. SURFACE AND GROUND WATER CONDITIONS 21. The first water-bearing zone (water table zone) beneath the Site occurs at a depth of 10 to 19 bgs. A shallow zone occurs at depths of approximately 50 to 100 feet bgs. An intermediate water-bearing zone occurs at depths of 100 to 150 feet bgs, and a deep aquifer is present at depths of 150 to 200 feet bgs. Water level measurements across the site indicate that there is hydraulic connection between the water-bearing zones above the Corcoran Clay. Saline groundwater occurs in locations west of the Site. GROUNDWATER MONITORING 22. As part of the groundwater remedial action, the Discharger performs groundwater monitoring pursuant to Monitoring and Reporting Program (MRP) Order No. R5-2004- 0800.