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water monitoring wells during the pilot-source test showed vacuum <br /> influence across the entire lot with the exception of northwest <br /> corner near MW6. <br /> - RLCOMMENDATIONS <br /> 1. Continue the quarterly ground water sampling and <br /> monitoring for this site. <br /> 2. Perform intermittent pumping from monitor wells MW1 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 /> once 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 /> h b - `ound <br /> kt+'" d <br /> CITI may <br /> a a rsr�t The public hearing <br /> c rig interim ria a 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 extraction excluding the <br /> gauging of monitor well MW5 (slant drilled well) . The depth to <br /> ground water 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 gradit,.,t <br /> flowing to the southeast with a increase in slope from MW1 to MW2. <br /> This increase 1n slope (gradient) zs most likely attributed to a <br /> recharge cycle of the aquifer and the daming effect of the slower <br /> x' page 2 <br />