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Working To Restore Nature ' Report on Vapor Extraction Test January 29, 1993 Coca-Cola Former Distribution Facility, Stockton, California 5400601 ' In November 1990, the groundwater sample from newly constructed well MW-6 indicated nondetectable concentrations of TPHg, and BTEX TPHd was detected at a concentration 1 of 64 ppb Preliminary Vapor Extraction Test In November 1990, a preliminary vapor extraction test was conducted to determine the feasibility of using vapor extraction as a soil remediation alternative (USTEC, September j 1991) The test was conducted on VEW-1 through VEW-4 and MW-1, MW-4, and MW-5 Applied wellhead vacuums ranged from about 50 to 66 inches of water Induced vacuums in the observation wells were measured, and ranged from 0 1 to about 6 inches of water Distances between wells ranged from 12 5 to 94 5 feet Extracted soil vapor concentrations were not determined, nor was the effective radius of influence One year later in November 1991, four additional vapor extraction wells (VEW-5 through VEW-8) were installed. These four new wells were not previously tested for a soil vapor extraction system Boring logs for these four wells were included in the fourth quarter 1991 monitoring report (USTEC, 1992), but results of soil laboratory analyses for these vapor wells were not available to RESNA at this writing Ouarterlv Groundwater Monitoring ' Ouarterly groundwater monitoring was initiated after the wells were installed Appendix A, Table A-4 summarizes depth-to-water (DTW) measurements and groundwater elevations ' DTW ranges from about 67 feet to about 75 feet, and groundwater elevation is averages about 52 feet below mean sea level (MSL) The groundwater flow direction is generally toward the northeast, at a shallow gradient of about 0 002 feet per foot As of December 1992, seven quarters of groundwater monitoring have been conducted The cumulative results of laboratory analyses of groundwater samples are reported in Appendix A, Table A-3 In California, TPHg and TPHd in groundwater are regulated indirectly through the petroleum hydrocarbon constituents, benzene, toluene, ethylbenzene, and total ' xylenes. Toluene, ethylbenzene, and total xylenes have been within State and Federal MCLS for all seven quarters in all six wells, and ranged from nondetectable to 3 1 ppb Benzene has been within the MCL (of 1 ppb) in MW-4 and MW-6 for all six quarters In MW-1 benzene concentrations have ranged from nondetectable to 40 ppb, in MW-2 from nondetectable to 7 9 ppb, in MW-3 from nondetectable to 3 9 ppb, and in MW-5 from nondetectable to 3 0 ppb as seen in Table A-3 State and Federal regulatory limits are reported at the bottom of Table A-3 A soil cleanup may be adequate to bring benzene concentrations within the MCL on a long term basis, since at present benzene 1 6