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CLOSURE REQUEST 5-31-94 <br /> 3436 pounds of gasoline range hydrocarbons and is based upon <br /> confirmation sample borings SB3 . .SB12, which were drilled and <br /> sampled on July 20, through July 22 , 1992 . <br /> A final estimate of 531 pounds of hydrocarbons remained in the <br /> soil on February 2, 1994 from sample results obtained from <br /> confirmation soil sample borings SB13 , SB14 and SB15 . <br /> Review of the past history of the site, Indicates the only <br /> pollutants of concern would be associated with gasoline . <br /> II. INVESTIGATIVE METHODS <br /> a) Soil sampling methodology. <br /> In order to estimate the lateral and vertical extent of the <br /> petroleum contamination at the site; 123 soil samples from 25 <br /> borings along with 28 soil samples obtained from the excavations <br /> were Chain of Custody delivered to DHS certified laboratories for <br /> analysis that included Total. Petroleum Hydrocarbons as gasoline, <br /> kerosene, diesel and oils Benzene, Toluene, Ethylbenzene, <br /> Xylenes, Tetra Ethyl Lead, Total Lead, and Ethylene Dibromide <br /> (EDB) , see Table 4 and Figures 3A, 3B, 7A, 7B, 7C and 7D <br /> Ground water monitoring well Installations occurred in stages, as <br /> more information was developed from monitoring the site The <br /> initial monitoring wells (MW1, MW2 , MW3 and MW4) were Installed <br /> between December 4 and December 8 , 1989 Two additional ground <br /> water monitoring wells (MW5 , a slant well beneath the store <br /> building and MW6) were installed on August 8 and 9, 1990 The <br /> need to define the ground water extent in a south to southeast <br /> direction dictated the Installation of the last monitoring well <br /> (MW7) on July 21, 1992 <br /> REMEDIATION-Contaminated Native Soil <br /> After the initial tank removal and sampling that occurred on <br /> September 29 , 1989, the UST cavity was over-excavated to the 26 <br /> foot depth and samples obtained on June 26 , 1990, see Table 4 and <br /> Figures 7A and 7B All the samples were "non detect" (less than <br /> 10 ppm) for Total Petroleum Hydrocarbons (TPH) Minor amounts of <br /> toluene, ethylbenzene, and xylenes were present In the sample <br /> taken from the center of the excavation EX-5 and minor amounts of <br /> xylenes were found In the samples taken at the southeastern edge <br /> of the excavation EX-A and EX-B The results of soil analyses <br /> from the placement of the two additional monitor wells (MW5 and <br /> MW6) were all below detection limits for TPH and BTEX with the <br /> exception of the sample obtained from MW5 at the true vertical <br /> depth of 33 feet, which had minor amounts of toluene and xylenes . <br /> Excavating of the pump island area commenced on August 16, 1990 . <br /> Using Manley and Sons backhoe and operator, three trenches were <br /> cut to the six foot depth through each of the three Island areas, <br /> paralleling Harding Way. The excavated soil from these cuts were <br /> screened by a WEGE geologist for odor and with a HNu photoionizing <br /> page? <br />