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3.4 Wel! Surve ' A well survey was previously conducted by RESNA Industries, Inc to identify wells within 2,000 feet of the site Results of the survey indicated that there were two domestic wells approximately 1,000 feet north of the site and two momtormg/test wells approximately 1,000 west of the site Well locations are shown on the figure included m Appendix C Well logs were not available for these wells t3_5 Remedial Actions ' 3.5.1 Groundwater Remediation In October 1989, the Bio National Corporation began extracting groundwater from MW-1 The extracted groundwater was stored in a 350-gallon tank and treated using oxidation and filtration procedures The treated groundwater was then stored in a 6,000-gallon baker tank The rate of groundwater extraction from well MW-1 was 3 liters per hour Approximately 1,750 gallons of groundwater was extracted and treated on-site using an Advanced Oxidation Unit from October 1989 to April 1990 The treated water contained no detectable concentrations of TPHg, TPHd, BTEX, MTBE, or HVOCs Details of the groundwater treatment program are contained in Bio National Corporation's Report on Extraction and Treatment of Contaminated Water and Biological Treatment of Collected Cuttings, dated May 30, 1990 Due to the slow rate of groundwater recovery (3 liters per hour), active groundwater remediation was not continued at the site Natural biodegradation of petroleum constituents was monitored by conducting groundwater monitoring and sampling activities Wells MW-3, MW-4, and MW-6 have never contained detectable concentrations of TPHg or BTEX since their installation in 1990 Well MW-6 has contained an unidentified hydrocarbon in the TPHd range MW-2 has not contained TPHg or BTEX since February 1990 Since the excavation activities in September and October 1995, ' detectable concentrations of BTEX and HVOCs have been below the California Primary Maximum Contaminant Levels(MCLs) iFrom December 1990 to June 1995, RESNA removed free product from well MW-1 during quarterly monitoring activities A total of approximately 20 ml of free product and 7 gallons of free product mixed with water was hand bailed from the well With the approval of PHS/EHD, the free product was placed to an aboveground waste oil tank and subsequently disposed of as used oil ' During September and October of 1995, approximately 8,406 cubic yards of soil was excavated The limits of the excavation are shown on Figure 4 The bottom ten feet of the excavation contained groundwater and with the approval of the City of Stockton approximately 400,000 gallons of ' groundwater was pumped from the excavation into the City of Stockton sewer system iw 19433]\closure&c 4 M SNtTH