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4.0. PREVIOUS SUBSURFACE INVESTIGATION <br />' The following is a summary of previous investigations at the site of the unauthorized release of fuel <br /> products to the subsurface <br /> a December 1994 - Five soil borings (B-1 through B-5) were advanced at the site near the <br /> former UST areas to depths of 65 feet below surface grade (bsg) Petroleum hydrocarbon- <br /> impacted soil was encountered in all five soil borings at depths between 10 and 65 feet bsg <br /> Results of the December 1994 investigation were reported in Preliminary Investigation and <br /> Evaluation Report(PIER),dated 10 April 1995,prepared by Geological Audit Services,Inc <br /> I0 January 1995 - Three ground water monitoring wells (MW-1, MW-2 and MW-3) and one <br /> soil boring (B-6) were advanced at the site as part of site assessment activities Soil boring <br /> B-6 was advanced to a depth of 65 feet bsg, wells MW-1, MW-2 and MW-3 were advanced <br /> I to depths of 80 feet bsg Petroleum-impacted soil was encountered in all four boring <br /> locations at depths between 35 feet and 65 feet Dissolved TPH-g and BTEX compounds <br /> were detected in initial ground water samples from all three wells at concentrations up to <br />' 11,000 micrograms per liter (µg11) Results of the December 1994 investigation were <br /> reported in Preliminary Investigation and Evaluation Report (PIER) dated 10 April 1995, <br /> prepared by Geological Audit Services, Inc <br />' 0 December 1995 - Three soil vapor extraction (SVE) wells (VW-1, VW-2 and VW-3) were <br /> advanced to depths of 63 feet bsg near the former UST areas, one ground water monitoring <br /> I well (1\4W-4)was advanced to a depth of 75 feet bsg and located in the warehouse building <br /> structure, approximately 60 feet southeast of the former UST area TPH-g and BTEX- <br /> impacted soil was encountered in all three SVE wells at depths between 15 feet and 60 feet <br />' at concentrations as high as 7,400 mg/kg, petroleum hydrocarbons were not detected in soil <br /> samples collected from MW-4 Dissolved TPH-g was not detected in initial ground water <br /> samples collected from MW-4 Results of the December 1995 investigation were reported <br />' in Corrective Action Plan (CAP), dated 20 March 1996, prepared by AGE <br /> • January 1996 - One ground water monitoring well (MW-5) was advanced off-site, <br />' approximately 50 feet northwest of the former UST area to a depth of 70 feet TPH-g and <br /> BTEX-impacted soil was encountered at depths of 45 and 50 feet at concentrations as high <br /> as 940 mg/kg TPH-g and BTEX-impacted ground water was detected in the initial sample <br />' from MW-5 at aconcentrationof23,000µg/1 Results of the January 1996 investigation were <br /> reported in the CAP <br /> An 8-hour SVE pilot test was conducted at the site by inducing a vacuum from well VW-1B <br />' (screened 28 to 43 feet bsg) The pilot test was performed to provide vapor extraction data <br /> for proper system design of an SVE remediation system TPH-g and BTEX compounds were <br />' detected from influent SVE air flow samples at concentrations as lugh as 95,000 micrograms <br /> µg/1 Based on the observed results,a theoretical radius of influence for SVE at VW-1 B was <br /> projected at approximately 30 feet Results of the January 1996 investigation were reported <br />' in the CAP <br /> . 0 April 2000-Five soil borings(CPT-1,CPT-1 A,CPT-2,CPT-2A and CPT-3)were advanced <br />' APPENDIX A <br />