Laserfiche WebLink
June 13, 1997 <br /> Page 6 <br /> concentrations of the analytes were reported The excavated soil was transported to <br /> Forward Landfill in Stockton (GSI, 1992) <br /> RECENT INVESTIGATIONS <br /> Quarterly Groundwater Monitoring <br /> Quarterly groundwater monitoring was initiated during the fourth quarter of 1990 by <br /> GTI Quarterly reports have been prepared by GTI from August 1990 to August 1994 <br /> and by Blaine Tech Services (Blaine) from November 1994 to November 1996 <br /> Historical groundwater monitoring data for site wells are reported in the Fourth Quarter <br /> 1996 Monitoring report by Blaine (Attachment E) <br /> Historically, Well MW-3 was reported with the highest concentration of TPH-g and <br /> benzene at 15,000 ppb and 890 ppb on August 20, 1990 TPH-g and BTEX in Wells <br /> MW-2 through MW-4 have been reported non-detect for the past five quarters of <br /> monitoring In addition, non-detectable concentrations of MtBE have been reported for <br /> the past two quarters in Wells MW-2 through MW-4 <br /> Historically, the predominant groundwater flow direction has been to the northeast <br />. EXTENT OF HYDROCARBON PRESENCE IN SOIL AND GROUNDWATER <br /> Based on the results of previous investigations performed at the site and the results of <br /> UST, and product line and dispenser removal activities, it appears that a majority of <br /> petroleum hydrocarbon impacted soil has been remediated through the various soil <br /> excavation activities Remaining residual hydrocarbons are expected to naturally <br /> attenuate over time <br /> Low to non-detect concentrations of TPH-g and benzene were reported in soil samples <br /> collected from Borings/Wells MW-1 through MW-4 In addition, five recent <br /> consecutive quarters of groundwater monitoring report non-detect TPH-g and BTEX <br /> concentrations in Wells MW-2 through MW-4 Well MW-1 was buried under the <br /> existing building foundation in August 1994 <br /> RATIONALE FOR SITE CLOSURE <br /> In summary, PACIFIC believes the site is a good candidate for closure Our request for <br /> closure or no further action status for this site is based on the following rationale <br /> All USTs, product lines and dispensers were removed from the site by the end of <br /> 1991 Approximately 615 cubic yards of impacted soil was excavated, 600 cubic <br /> yards of impacted soil was excavated, aerated, and reused as backfill, and 15 cubic <br /> yards of soil excavated and hauled to a San Joaquin County approved landfill for <br /> • disposal in D bei 1991 <br /> 9201036MCLOSURE DOC <br />