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Report 5 The So The Southland Corporation,9110 Thornton Road StxMon CA December 5 1995 20 REMEDIATION ACTMTIES 21 Groundwater Extraction and Separate-Phase Recovery Between May 1986 and August 1990,separate-phase hydrocarbon recovery and groundwater treatment systems were installed and operated by Groundwater Technology Approximately 780 gallons of hydrocarbons were recovered No separate-phase hydrocarbons have been detected at the site since August 1988 Groundwater extraction occurred at vanous times from MW-1, MW-4, MW-12, PW-1, PW-3, and RWA Approximately 1 6 million gallons of groundwater were extracted and treated Groundwater capture dunng extraction from PWA and RW-1 Is Illustrated on the potenttometnc surface map for July 26, 1988 (Figure 5) 22 Soil Vapor Extraction Between February 1987 and January 1991, a SVE system was installed and operated The SVE system removed the equivalent of 576 gallons of separate-phase hydrocarbons SVE was conducted at various times from VP-1,VP-2,VP-3,VP-4, RWA, MWA, MW-3, and MW-4 Approximately 209 • million cubic feet of air/vapor was extracted and treated Operation of the system was discontinued after hydrocarbon vapor concentrations reached apparent asymptotic levels 30 CONFIRMATION SAMPLING Confirmation sampling at the Stockton site has been conducted by continued quarterly monitoring and sampling of monitonng wells, a final round of sampling of neighboring domestic wells, and drilling of 16 sal confirmation bonngs dunng two different events Results of confirmation sampling are discussed In Section 4 0 Methods associated with quarterly groundwater monitoring are descnbed In quarterly monitoring reports (e g Third Quarter Monitoring and Sampling Report, Groundwater Technology, Inc , August 10, 1995) Methods used dunng dnlitng of the first nine soil confirmation bonngs are descnbed in a previously submitted closure report for the site (Closure Report, Groundwater Technology, Inc , May 21, 1993) Methods used for domestic well sampling and dnlling of the last seven soil confirmation bonngs are presented below 3 1 Domestic Well Sampling Domestic well sampling was conducted on July 31, September 6, and September 27, 1995 Groundwater samples were collected from water taps hooked up to domestic wells in the presence of Mary Meays of SJCPHS-EHS Collected samples were labeled,stored on ice In an Insulated container, ciosurez rw(sTHL.a 1) ❑�C GIi0UNI) warn? ❑�� TI-CHN01 OG)