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6.0 SPECIFIC INFORMATION FOR CLOSURE REQUEST <br /> ' EJ Introduction <br /> This section provides information specifically required for closure review as per the October 7, 1993 <br /> Addendum to Appendix A of the Tri-Regional Reconunendations <br /> 6k2 Rationale for Closure <br /> ' Based on the ul analytical results s is of the confirmation soil samples collected in November 1993, <br /> and the trend of decreasing contamination in the groundwater monitoring wells to <br /> nondetectable levels, it appears that TPHg and BTEX in soil have been remediated to <br /> concentrations at nondetectable levels The contaminated soil, the source of the groundwater <br /> contamination, was removed and remediated to nondetectable levels in November 1993. <br /> Approximately 54,000 gallons of contaminated groundwater was removed and disposed of in <br /> April 1994, prior to backfilling the excavation Since the remediation of the soil and the <br /> disposal of the groundwater, MW-2, MW-3, and MW-4 have contained no detectable <br /> concentrations of petroleum hydrocarbons MW-1R has exhibited decreasing concentrations of <br /> petroleum hydrocarbons constituents to nondetectable levels since its installation. <br /> 6_3 Site Specific Information Summary <br /> o Sixty-four groundwater wells are known to exist within 1 mile of the site, based upon <br /> information provided by the Department of Water Resources (DWR) The wells <br /> consist of thirty-four monitoring wells, seven domestic wells, seven industrial wells, <br /> four test wells, one gas well, and one irrigation well Ten of the sixty-four wells listed <br /> did not identify the type of well Records indicate a domestic well approximately 0 25 <br /> mile due east of the project site <br /> o Depicted n <br /> p o enclosed figures are the site location and nearby surface waters (Figure 1), <br /> the site to scale and former tank locations (Figures 2 and 4), well and boring locations <br /> (Figures 2), most recent groundwater gradient contours (Figure 3), and the excavation <br /> area/former area of impaction in the soil(Figures 5 and 6) <br /> o Water level data are presented in Table 1 During the investigative history of the site, <br /> depth to groundwater has ranged from 5 19 to 19 14 feet below grade <br /> o Tables 3 and 4 present the soil analytical results and Table 2 presents the groundwater <br />® analytical results <br />■ o Solt remediation methodology is described in Section 3 4 Remedial Actions Natural <br /> biodegradation and aeration were used to remove petroleum hydrocarbons from the <br /> excavated soil on-site <br /> w 19433ftIos=dm 7 <br /> 1 � <br /> t <br /> SWFH <br />