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T Cobb Environmental & Technical Services . QUARTERLY GROUNDWATER MONITORING REPORT SECOND QUARTER 1997 E-Z Serve#100966, 2537 Waterloo Road, Stockton, CA BACKGROUND All underground storage tanks were removed in March, 1990 A total of eight monitoring wells (MW-1 through MW-8) and two vapor extraction wells(VE-1 and VE-2) have been installed, eight on-site(MW-1 through MW-5,MW-07, VE-1 and VE-2) and two off-site(MW-6 and MW-8) The extent of groundwater contamination has been delineated GROUNDWATER MONITORING FIELD ACTIVITIES Date of Field Activities 6120197 Wells Momtored/Sampled MW-I through MW-8 Analytes Tested TPHg, BTEX and MTBE Analytical Methods EPA Methods 8015/8020(modified) Laboratory Entech Analytical Labs, Inc Remarks In April the UST Cleanup Fund issued sampling protocol recommendations based on a study performed by the WSPA This recommendation, coupled by the many sampling events which preceded the second quarter 1997, has resulted in E-Z Serves decision to evaluate the suitability of the no-purge method of sampling All samples collected during the second quarter utilized the no-purge method sampling GROUNDWATER MONITORING RESULTS Depth to Water 52 04 to 52 7 feet below grade Flow Direction/Gradient Southwest at 0 0002 ft/ft SPH-wells/thicknesses Not Detected TPHg concentration range <50 ppb(MW-1,4,5,6, and 8)to 80,000 ppb(MW-2) Benzene concentration range <0 5ppb(MW-1,4,5,6, and 8)to 29,000 ppb(MW-1) MTBE concentration range <5 Oppb(MW-1,2,3,4,6,7, and 8)to 7 5 ppb(MW-5) Remarks Groundwater flow is generally consistent with previous measurements Groundwater dropped an average of 4 feet across the site since the last sampling event Groundwater is above all well screens Due to this condition all wells will be purged during the third quarter sampling PROJECT STATUS Third Quarter monitoring will utilize the purge technique for sampling all wells The vapor extraction wells will be purged and sampled to determine concentrations present in the upper portion of the aquifer Based on the results of this additional sampling a proposal to install additional shallow monitoring wells and/or a strategy for corrective action will be prepared ATTACHMENTS• • Groundwater Elevation Contour Map • Groundwater Elevations and Analytical Results(Table 1) • Laboratory Report and Chain-0f-Custody form • Groundwater Monitoring and Sampling Protocols • Gauge/Purge Calculations and Well Purging Date Sheets • Purge vs No-Purge Protocol P Q Box 1602 • Tupelo, Mississippi 38802-1602 601-841-0995 (phone) • 601-841-0810 (fax)