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,,psi� ,,r <br /> wE•.^x""�` - "*"' !� <br /> Ms. Diane Hinson <br /> March 6, 1990 <br /> Page 8 <br /> Summary <br /> Soil sample analytical results indicate that TPH(g) was present at detectable concentrations in soil <br /> sample collected from borings for monitoring wells MW-2, MW-3, MW6, and MW-7 at depths <br /> ranging between 21 and 26 feet below grade. TPH(g) concentrations ranged from 1.3 ppm (MW-3 <br /> at 26 feet below grade) to 110 ppm (MW-7 at 31 feet below grade). <br /> Analytical results of ground water samples collected from monitoring wells MW-1, MW-3, MW-a, <br /> MW-5,and MW-6 indicate that benzene is present only in MW-3 and MW-4 at concentrations of 0.030 <br /> ppm and 0.025 ppm, respectM ly. <br /> Ground water is present at depths ranging from 28.28 to 30.97 feet below grade- The inferred <br /> direction of ground water flow is toward the north with an approximate gradient of 0,019-foot per foot. <br /> Free-floating petroleum product was first recorded in monitoring wells MW-2 and MW-7 at <br /> thicknesses of approximately 4,45 and 0.71-feet,respectively. Free product is being removed by bailing <br /> from monitoring wells MW-2 and MW-7 on a weekly basis. The most recent bailing event indicated <br /> that free product has been reduced to a thickness of 3.87 feet in monitoring well MW-2, and that no <br /> free product remains in MW-7. Figure 7 illustrates the approximate on-site distribution of free <br /> petroleum product. <br /> Future Wnrk <br /> An interim remedial action plan is presently being developed. A manifold piping system to convey <br /> compressed air, ground water discharge, and soil vapor vacuum lines is currently being installed to <br /> provide for future remediation (i`igure 8). In the meantime,an air operated automatic free product <br /> skimming pump will be installed to remove product from monitoring well MW-2. <br /> The site is currently undergoing construction. As soon as the area above the new tanks is accessible, <br /> proposed vapor extraction weW (MW-8 and MW 9)will be installed. <br /> Sincerely, <br /> DELTA ENVIRONMENTAL CONSULTANTS, INC <br /> Charles Keoni Almeida <br /> Project Geologist \�.1% R D G <br /> Vq1A, tip 4Otp% <br /> Erin Dougherty <br /> Project Manager NO. 46.2 t. <br /> p <br /> Daly: A. van Dam, R.G. <br /> F-Mrugcologist Of CAI.EF�� <br /> CKA:Iaw <br />