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v <br /> rs A S 5 0 C I A T E S I N C <br /> f r__ <br /> contamination. Results of soil samples collected in the vadose zone (less than 11 feet deep) suggest <br /> that shallow soil contamination was somewhat random and not laterally continuous across the site. <br /> r'= <br /> Furthermore, no BTEX constituents were present at significant levels. <br /> In September 1999, ATC supervised the advancement of soil borings S13-11, SB-12, and SB-13 at <br /> locations approximately 15 feet northwest, south, and northeast of well MW-4, respectively. <br /> Analytical data indicated the groundwater sample from soil boring SB-12 was impacted with TPHd at <br /> a concentration of 24,000 ppb. The groundwater samples from SB-11 and SB-13 contained very low <br /> r� to nondetectable concentrations of TPHd. Results of laboratory analyses performed on selected soil <br /> samples indicate that TPHd was present in only the samples collected between 14 and 16.5 feet bgs. <br /> ;`- Field observations indicated that the samples at these depths also exhibited the highest FID <br /> measurements. Soil samples S1311-15.5, SB12-16.5, and SB13-14.0 contained detectable <br /> concentrations of TPHd at 390 ppm, 290 ppm, and 1,100 ppm, respectively. All the remaining soil <br /> F samples were not detected. The September 1999 subsurface investigation activities are detailed in <br /> :. <br /> ATC's Summary Report, Subsurface Investigation, dated January 10, 2000. <br /> A groundwater pumping test was conducted during a 24-hour period starting on July 22, 1999 and <br /> F j ending July 23, 1999. The goal of the groundwater pump test was to provide aquifer data necessary to <br /> characterize the feasibility of operating a groundwater treatment system at the site. The radius of <br /> influence of groundwater extraction, groundwater drawdown, hydrogeologic properties of the aquifer, <br /> and the mass extraction rate of groundwater were to be determined by this pumping test. The results <br /> of the groundwater pumping test showed the radius of influence for groundwater extraction at the site <br /> is greater than 50 feet. Hydrogeologic properties of the aquifer, specifically, hydraulic conductivity <br /> (K), transmissivity (T), and the coefficient of storage (S) were measured. The average hydraulic <br /> conductivity (K) was calculated to be 0.001 meters/second, the average transmissivity (T) was <br /> `s calculated to be 6.79 square feet/minute, the Coefficient of Storage (S) was calculated using Cooper- <br /> Jacob solution to be 0.0015. In addition, based on analytical results of samples taken during the <br /> groundwater pumping test, 6,000 gallons of groundwater were extracted from the subsurface, and <br /> 0.00005 lbs. of TPHd were removed from the subsurface during the twenty-four hour test. The <br /> groundwater pumping test activities are detailed in the Summary Report of Pumping Test, dated <br /> F f September 19, 2000. <br /> w:s <br /> 4.0 EXISTING CONDITIONS <br /> r_ <br /> 4_1 Sail Conditions <br /> 4.1.1 Site Geology <br /> The site consists of primarily lean clays , silty clays, with areas of silty sand. Poorly graded gravels <br /> were encountered at the surface to depths of approximately 3 feet in some areas. Lean clays, silty clays <br /> _= and in some areas, silts, were encountered ranging from the surface to 5 feet bgs to depths of <br /> approximately 11 to 16 feet bgs. Silty sands were encountered from about 16 feet to depths of 36 feet <br /> bgs, the maximum extent borings were advanced. <br /> w:162574.021reportslclosure-smilh.doc 3 <br /> Gr� <br /> �r <br />