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1 <br /> C L E A17R�-W'IA T E R <br /> G R O U P, I N C <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> The following conclusions were made on the basis of data obtained during this <br /> preliminary site investigation <br /> • Subsurface materials at the site consist primarily of poorly graded sand, silty and <br /> Y �' ty <br /> clayey sand, and lean clay, the strata appear to be laterally heterogeneous above a <br /> depth of 30 feet bgs <br /> • Depth to groundwater is approximately 52 feet bgs (-6 feet mean sea level) <br /> • Groundwater flow at the site cannot be estimated on the basis of only two wells, <br /> but the gradient between BMW-1 and BMW-2 is approximately 0 004 feet/foot <br /> • TPHg, BTEX, and TPHd were not detected in soil samples collected from the <br /> vadose zone (between 9 5 feet bgs and 49 5 feet bgs) in either boring <br /> a MTBE was detected in soil samples collected between 24 5 and 39 5 feet bgs at the <br /> BMW-1 location (near the UST basin) and between 44 5 and 49 5 feet bgs at the <br /> BMW-2 location (near the southern dispenser island), maximum concentrations <br />' detected were 0 15 ppm <br />' • Groundwater samples from both monitoring wells contained TPHg, BTEX, <br /> MTBE, and TPHd, the highest analyte concentrations were in the groundwater <br /> sample from BMW-1 <br /> On the basis of the data obtained during this investigation, additional site <br /> assessment is recommended for the following reasons <br /> 1 * Analysis of soil samples y p es collected near potential source areas indicate that TPHg, <br /> BTEX, and TPHd were not detected, although MTBE was detected at both boring <br /> locations - - -- <br /> • Groundwater samples contained fuel hydrocarbons and generally the soil <br /> samples from the vadose zone did not, indicating either an offsite source or an <br /> unidentified onsite source <br /> C-115 PRE AR 10/95 7 October 11,1995 <br />