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z 31 October 1996 - AGE-NC,Project No 95-0113 IPage 3 of 4 ' and B4 were advanced to a depth of 15 and 20 feet, respectively Boring MW-1 was advanced to a depth of 40 feet and converted into a 2-inch diameter ground water monitoring well ' A total of ten soil samples were submitted to the laboratory for analysis TPH-g and BTE&X were detected in Sample B1-10, TPH-g at 260 ppm and BTE&X up to 31 ppm Sample B2-15 was found to contain 3 1 ppm of TPH-g and up to 0 43 ppm of BTE&X Total lead was also detected at 230 ' ppm in B 1-10 However, the extraction analysis for the above mentioned sample yielded a result of 2 7 ppm, below the Soluble Threshold Limit Concentration (STLC) No TPH-g or BTE&X were detected in the ground water sample collected from MW-1 ' Thep g rocedures and results of the investigation were detailed in AGE report, Preliminary Investigation and Evaluation, dated 20 July 1995 Analytical results of all soil samples are ' summarized on Table 1 The laboratory report (MAI Laboratory ID Nos 52690 to 52701 and 52873) QC report and chain-of-custody are included in Appendix B ' MW-1 was subsequently sampled on 18 August 1995 by AGE TPH-g and BTE&X were not detected in this sample as well The laboratory report (MAI Laboratory ID No 55547), QC report and chain,of-custody are included in Appendix C ' 5 0. DISCUSSION AND RECOMMENDATIONS Based upon the existing data, AGE presents the following discussion and recommendations ' As indicated by the analytical results of samples'collected following the tank removal, Sample N1, the release apparently took place in the northern portion of the tank excavation ' Based on the results of the preliminary subsurface investigation, the lateral extent of the hydrocarbon-impacted soil appears to be limited. The inferred lateral extent of the impacted soil is depicted on Figure 3 - Estimated Extent of Hydf ocarbon Impact in Soil ' Vertically, the extent appears to be limited as well Based on the non-detection of hydrocarbons in the samples collected from depths of less than 10 feet below surface grade ' (bsg) during the tank removal, it appears the hydrocarbon release took place at the bottom of the tank(s), impacting soil at approximately 10 feet bsg The results of the subsurface investigation indicated that the maximum vertical extent of the impact appears to be limited ' to appioximately 15 feet bsg • Based on the estimated lateral and vertical extents, the total volume of the impacted soil is ' calculated to be approximately 200 cubic yards , • During installation of MW1, the saturated zone was not encountered until approximately 26 t '