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FIELD REPORT <br /> QUARTERLY GROUNDWATER MONITORING <br /> SAN JOAQUIN COUNTY MOSQUITO ABATEMENT DISTRICT <br /> LODI FACILITY, LODI, CALIFORNIA <br /> On August 25, 1992, ROY F WESTON, INC (WESTON) conducted groundwater sampling <br /> at the San Joaquin County Mosquito Abatement District (SJCMAD) facility at 200 North <br /> Beckman Road, Lodi, California This field work was conducted to meet the requirements of <br /> the San Joaquin County Public Health Services, Environmental Health Division (EHD) <br /> Upon arrival at the site, measurements of the standing water levels were taken in all wells using <br /> an electronic well sounding device MW-2 and MW-3 were dry. Calculations to determine the <br /> Mean Sea Level (MSL) elevation of groundwater in MW-1 and MW-4 were made and the results <br /> Iare presented in Table B-1 <br /> TABLE B-1 <br /> Water Level Elevations <br /> August 25, 1992 <br />' Well Location Well Elevation Depth to Water Water Elevation <br /> (feet, MSL) (feet) (feet, MSL) <br /> MW-1 54 11 5428 -017 <br /> MW-2 5428 Dry Dry <br /> MW-3 5403 Dry Dry <br /> MW-4 5443 5974 -531 <br /> The total depth of each well was measured prior to collecting the groundwater samples Using <br /> the total depth and the depth to water, the standing water volume within the casing was <br /> calculated to determine the necessary purge volume. <br /> WESTON planned to purge a minimum of three well casing volumes from each well prior to <br /> sampling, but MW-1 was bailed dry after approximately one gallon (or 11/h well casing volumes) <br /> was removed from the well. The well was allowed to recover prior to sample collection <br /> To purge well MW-1, a clean teflon bailer was attached to new thin, braided, nylon line and <br /> lowered into the well to be filled Purge water was placed in a 55 gallon drum for storage <br /> onsite pending analytical results A clean submersible pump was used to purge MW-4 and as <br /> the well was pumped, the discharge rate was measured in order to calculate the time required <br /> to obtain three casing volumes. MW-4 was purged dry and allowed to recover four times <br /> Ultimately over three casing volumes (25 gallons) were removed and the well was allowed to <br /> fully recover prior to sampling At the beginning, during, and at the end of the purge process, <br /> measurements were taken for pH, electrical conductivity, and temperature of the purge water <br /> MXC\R I'SWCMAD WP B - 1 10112M <br />