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1 <br /> FIELD REPORT <br /> GROUNDWATER SAMPLING <br /> SAN JOAQUIN COUNTY HUMAN SERVICES AGENCY BUILDING <br /> STOCKTON, CALIFORNIA <br /> tIntroduction <br />' On August 2 and 3, 1991, ROY F WESTON, INC (WESTON) conducted a sampling program <br /> of five monitoring wells located in the vicinity of the San Joaquin County Human Services <br /> building in downtown Stockton This sampling was conducted in order to evaluate the possible <br />' presence of gasoline-related compounds in the groundwater <br />' Water Level Measurement and Monitor Well Puree <br /> On arrival at the site, measurements of standing water levels and total well depth were taken in <br />' all wells utilizing an electronic well sounding device Calculations to determine the water level <br /> Mean Sea Level (MSL) elevation were made and the results are presented in Table A-1 <br />' TABLE A-1 <br /> Water Level Elevations <br /> Feet Above MSL <br /> August 2 and 3, 1991 <br />' Well Location Well Elevation' Depth to Water Water Elevation <br /> (feet) <br />' MW-4 1346 51 74 3828 <br /> MW-5 12 83 4996 37 13 <br />' MW-6 13 17 5057 3740 <br /> MW-7 13.14 5244 39 30 <br />' MW-8 1376 5303 3927 <br />' 1 Based upon measurements made from top of PVC casing (TOC) <br />' The water level measurements were also used to calculate the required purge volumes for the <br /> monitor wells From these measurements the standing water volume within the well casing was <br /> calculated to determine the necessary purge volume of three standing water volumes A clean <br /> submersible pump was then lowered into the well As the wells were pumped, the discharge <br /> rate was measured at the beginning of the purge and the needed purge time calculated A <br /> minimum of three casing volumes was removed from each well prior to sampling MW-5 was <br /> purged dry once then allowed to recover before sampling This information was recorded on <br /> field data sheets and is summarized in Table A-2 <br /> ' A - 14 o61e7M <br /> RFTSrSfC WP <br />