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R604 :UPDATE 9-MARCH, 1992 <br />• 4 . As requested by San Joaquin County Health, obtain <br /> fecal coliform samples from MW3 , MW4, MW5 and MW6 on <br /> a monthly basis, until a baseline is established for <br /> the presence of fecal coliform; then sample these <br /> wells for fecal coliform, during the quarterly <br /> sampling. <br /> 5 . Once the vapor extraction system is aga.-n <br /> operational, continue weekly monitoring and sampling <br /> of the vapor stream using the GC-PID 10 S 50 <br /> chromatograph and .include the results in a monthly <br /> update status report. <br /> 6 . Drill two confirmation sample borings, one near P3 <br /> and the other near SB-2 , to obtain soil samples for <br /> certified laboratory analyses of TPH-BTEX, see <br /> Figure 4 . <br /> 7 . Destroy vapor recovery wells P1 , P3-Swarm and EX. <br /> LOCATION <br /> Regal Station 604 (parcel # 139-020-08 ) is located at 1448 N. El <br /> Dorado and Harding Way, Stockton, San Joaquin County, California. <br /> The site is in pro3ected section 2; T1N; R6E; MDB&M at <br /> approximately 14 feet above mean sea level . Initial drilling <br /> (November, 1989 ) encountered ground water at approximately 32 feet <br /> below sea level ( 47 ' below the surface) and flowing in an east to <br /> southeasterly direction, see figures 1, 2 , and 3A. <br /> UPDATE STATUS REPORT #9 <br /> WELL SAMPLING AND ANALYTICAL TECHNIQUES <br /> Depth to ground water measurements were obtained from all of the <br /> ground water monitoring wells on January 21, February 4, March 5 <br /> and March 31, 1992. Water samples were obtained from the <br /> monitoring wells, by a Western Geo-Engineers (WEGE ) geologist on <br /> March 5 , 1992 . Top of casing elevations, as documented in <br /> previous reports, were used. Depth to top of fluid and ground <br /> water measurements were obtained using a clean product water <br /> interface probe. The probe, lowered into the well attached to a <br /> tape calibrated in 0 . 1 foot intervals, signals at the contact of <br /> floating product and at the top of ground water. The measurement <br /> is obtained from the calibrated tape reading adjacent to a <br /> reference point on the casing. The probe as cleaned with <br /> trisodium phosphate soapy water, with a distilled water rinse, <br /> before measuring the next well . Measurements are started at the <br /> historically cleanest wells and progressed to the dirtiest wells. <br /> All depth to ground water measurements were obtained prior to <br />. purging the wells for sampling. The depth to water -is then <br /> subtracted from the elevation of the casings reference point for a <br /> corrected ground water elevation The ground water gradient <br /> page 2 <br />