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4 <br /> THIRD QUARTER, 1997 <br /> GROUNDWATER MONITORING REPORT <br /> USA STATION#65-LODI '!p <br /> AUGUST;1997 <br /> 3.0 SCOPE OF WORK <br /> The following is a brief summary of the scope of work performed by GHH,' <br /> iwhch included <br /> groundwater monitoring on July 10, 1997. <br /> • Locate and measure depths to groundwater in monitoring wells MW-1 through <br /> MW-8, S-1 and S-2; <br /> ii <br /> Purge a minimum of three equivalent well volumes of groundwater from each of <br /> � <br /> the sampled wells while monitoring� P g pH, temperature and conductivity; <br /> • Collect groundwater samples from the purged monitoring wells; <br /> r <br /> L Analyze water samples for TPH in the gasoline range (TPH G), BTEX and methyl- <br /> tert-butyl-ether(MTBE)using EPA Methods 8015 Modified and 8020, <br /> respectively; ands <br /> ys t, d <br /> • 3 Prepare this QMR for submittal to USA and the County. <br /> t <br /> 4.0 GROUNDWATER MONITORING <br /> The following section discusses field protocol used during data collection for this QMR. <br /> ,k. <br /> 4.1 Groundwater Elevations <br /> Prior to gauging depths to groundwater, the groundwater monitoring wells were checked for the <br /> presence of free floating hydrocarbon using an interface probe. Depths to groundwater <br /> measurements were then taken from each well from surveyed marks on the casing using an <br /> electric water level sensor or interface probe. Calculated groundwater elevations are presented in <br /> Table 1. The field data sheets are included in Appendix A. <br /> r,E <br /> A <br /> 4.2 Monitoring Well Purging <br /> The monitoring wells were purged using a 2-inch diameter submersible Gruridfos groundwater <br /> pump or disposable bailer, until a minimum of three equivalent well volumes'ofwater were <br /> removed from each well. Groundwater purged from the wells was placed into Department of <br /> Transportation (DOT) approved 55-gallon drums and stored on-site prior todisposalby USA. <br /> i �I <br /> To reduce Ithe potential for cross-contamination between wells, all purging arid sampling <br /> P l� g P g <br /> equipmentliwas washed in a trisodium phosphate solution and rinsed in potable water prior to each <br /> use. P <br /> C <br /> i 3. <br /> k <br /> E Y 1 <br /> f <br />� � q <br />