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1994 to an arbitrary datum of 25 feet above sea level Groundwater elevation data are <br /> presented in Table 2 <br /> L. Groundwater Sampling and Analysis <br /> ' On October 14, 2994, a groundwater sample was obtained from each on-site monitoring well. <br /> The sample was collected after purging and stabilization of EC, pH, and temperature Field <br /> ' development/purge logs are presented in Appendix IV <br /> ' Subsequent to purging, groundwater was sampled and transferred to appropriate sample <br /> containers, using clean, disposable bailers with bottom emptying devices to reduce <br /> volatilization Sample containers were then labeled with sample identification, placed on ice, <br /> ' and shipped under chain-of-custody to Argon Mobile Labs <br /> ' The water samples were analyzed by Argon Mobile Labs for BTEX, TPHg, and TPHd by <br /> EPA methods 8020 and modified 8015, respectively The method detection limits at Argon <br /> Mobile Labs for BTEX and TPHg/TPHd in water are 0.5 and 50 parts per billion (ppb), <br /> respectively. Groundwater analytical results are summarized in Table 3, and laboratory data <br /> sheets are presented in Appendix III <br /> 3.0 SUBSURFACE CONDITIONS <br /> Soils encountered beneath the site consist primarily of sand with varying amounts of silt and <br /> clay to a depth of 30 feet below grade, the maximum depth explored. An apparently <br /> ' discontinuous clay lens was noted at a depth of approximately 16 5 feet below grade in boring <br /> SB2 <br /> ' Groundwater beneath the site was first encountered at approximately 17 feet below grade. <br /> After well completion, the piezometric surface stabilized to approximately 15 to 16 feet below <br /> grade. Based on October 14, 1994 monitoring data (Table 2), groundwater flows to the <br /> northwest under a gradient of approximately 0 0031 ft/ft or 16 feet per mile. A groundwater <br /> ' gradient map for October 14, 1994 is presented on Plate 3 <br /> ' 4.0 STOCKPELED SOIL REMIEDIATION ASSESSMENT <br /> To evaluate and develop a remediation plan for the stockpiled excavation soil, RESNA <br /> personnel visited the site on December 9, 1994, and collected eight additional 4:1 composite <br /> soil samples from the stockpile at depths ranging from two to three feet below the surface. <br /> i <br /> 1501071SR-0295 4 Ca n01'ileEnvlronmF <br />