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i <br /> 4 COMPILATION OF DATA IN SUPPPORT OF CASE CLOSURE <br /> Based on the analytical results for the confirmation soil borings, the following data are compiled <br /> in support of a request for case closure <br /> 41 SOURCE REMOVAL <br /> A review of the analytical results for soil andoundwater les collected at the site indicate <br /> �' samples <br /> that the two potential sources of petroleum hydrocarbons were (1) the former USTs, and the <br /> 1 associated product piping, and (2) the vadose soil beneath the USTs The removal of these two <br /> potential sources is discussed below <br /> 4.1 1 Tank Removal F <br /> i <br /> There have been two generations of underground storage tanks at the site The existing 20,000- <br /> gallon double-walled fiberglass UST with two compartments is located on the northern portion <br /> of the site (Figure 2) The three former USTs thought to be a potential source were 10,000- <br /> gallon single-walled steel tanks which were removed on 10 June 1992 During UST and <br /> associated piping removal, two confirmation soil samples were collected from beneath the ends <br /> of each of the three tanks at 16 feet bgs, as well as from beneath former product piping at 20 <br /> linear foot intervals The locations of these soil samples are shown on Figure 6, and the <br /> analytical results are summarized in Table 2 The manifests for the tank disposal are included in <br /> Appendix F <br /> The table below presents known information concerning the two generations of tanks at the site <br /> Installation Size Removal Tank <br /> Tank ID Date Construction (gallons) Date Contents <br /> A 1954 * SingleWall 10,000 6/10192 Regular—Leaded <br /> Steel Gasoline <br /> B 1954 * SingleWall 10,000 6/10/92 Regular— Unleaded <br /> Steel Gasoline <br /> C 1954 * SingleWall 10,000 6/10/92 Extra—Unleaded <br /> Steel Gasoline <br /> D 1993 * Double- 20,000 In Use 2 compartments, w/ <br /> ' walled 60 & 40% capacity <br /> Fiberglass Unleaded Gasoline <br /> * Approximate <br /> 4 1.2 Remediation of Vadose Zone <br /> As detailed in Section 2 4 2, the SVE system has removed approximately 1,551 pounds of TPH-g <br /> from the original start-up in November 1995 to March 1998 Touanti the effectiveness of the <br /> q fy <br /> remedial effort, five confirmation soil borings were drilled in August 1999 The locations of <br /> four of the five confirmation soil borings, SB4-SB7, were placed in the former UST backfill to <br /> allow for a direct comparison with soil samples collected before operation of the SVE system <br /> F IPI aj ect970137%,\1astei\WpN0ns,,re 11007 137uyent doc 9 <br /> i <br />