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s <br /> — y <br /> �s <br /> water monitoring wells during the pilot-source test showed vacuum <br /> i influence across the entire lot with the exception of northwest <br /> corner near MW6. <br /> RECOMMENDATIONS <br /> 1. Continue the quarterly y ground water sampling and <br /> i monitoring for this site. <br /> {� 2. Perform intermittent pumping from monitor wells Mwi and <br /> MW5 to control the spread of the hydrocarbon plume using Lawrence <br /> vacuum pump and removing approximately 50 gallons from both wells <br /> o=e a week. Store this water on site in 55 gallon drums until <br /> permission can be obtained for disposal. <br /> 3. Perform a cost benefit analysis to determine the most <br /> cost effective means for treatment of vapors from a vapor <br /> extraction-water treatment system. <br /> 4. Perform a cost benefit analysis to determine the most <br /> effective means of ground water treatment. <br /> UPDATE STATUS REPORT #6 (JANUARY 4 THRU JULY 9, 1991) . <br /> WESTERN GEO-ENGINEERS (WEGE) sampled and measured depth to ground <br /> water from all of the =site monitoring wells . during the <br /> monitoring rounds conducted on March 29 and June 24, 1991. . Also <br /> during this time frame a Petition for an Interim Variance for <br /> vapor extraction was executed and on .March 29, 1991 a .41 day <br /> Temporary Permit to Operate was granted. The public hearing <br /> concerning the Interim Variance occurred on May 9, 1991. Vapor <br /> extraction commenced at this site on April 26, 1991, see Appendix <br /> A. <br /> GROUND WATER MONITORING <br /> Ground water monitoring rounds were conducted on March 29 and June <br /> 24, 1991. During these visits, depth to ground water was measured <br /> and samples were obtained from the six on site monitor wells for <br /> chemical analysis. From this data, ground water gradient maps <br /> were generated, Table 1, Figures 4A and 4B. Figure 4A (3-29-91) <br /> uses the data obtained prior to vapor ex}raction excluding the <br /> gauging— of monitor w...ell _-MW5--(slant._drilled-well-)_. ...-The--depth—to ------ ---- - <br /> of this well does not represent actual depth to <br /> ground water. due .to the nature Of well installation and produces <br /> an .anomalous ground water high. Figure 4A shows a gradient <br /> flowing to the southeast with a increase in slope from MW1 to MR2. <br /> This increase in slope (gradient) is most likely attributed to a <br /> recharge cycle of the aquifer and the darning effect of the slower <br /> i <br /> page 2 <br />