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05 September 2002 AGE-NC Project No. 99-0605 — Page 3 of 6 4.0. SITE ASSESSMENT On 20 February 2001, four soil borings (B-I through B-4) were advanced at the site as part of the site assessment. Boring B I was advanced to a total depth of 35 feet bsg, borings B3 and B4 were advanced to a total depth of 30 feet bsg and boring B2 was advanced to a total depth of 70 feet bsg, from which a grab ground water sample was collected. In general,the dominant soil type encountered in the borings was brown to gray silt. Apparently laterally discontinuous sand or silty sand was encountered at 15 feet bsg in borings B3 and B4, and between 25 feet bsg to 35 feet bsg, 55 to 60 feet bsg and at 70 feet bsg in boring 132. Boring logs are included in Appendix A. A total of eleven soil samples and grab ground water sample were analyzed. Laboratory analytical results indicate: • MTBE was detected in soil samples B2-20, B2-30 and 132-40 at concentrations of 120 rnicrograms per Vvlligram (µg/mg), 1,200 gg/jAg and 63 jg/mg, respectively. MTBE - contamination was limited to samples collected between 20 feet and 50 feet bsg from soil boring B-2, located within the former UST excavation. TPH-g, TPH-d, THP-mo, BTEX, DIPS, ETBF, TAW.,TBA,methanol,ethanol,EDB and 1,2-DCA were not detected above laboratory reporting limits in any of the soil samples submitted for analysis. • Grab ground water sample B2 contained TPH-mo at a concentration of 360 micrograms per liter (pg/1), while TPII-g, TPII-d, MTBE, BTEX, DIPS, ETBF,, TAME, TBA, methanol, ethanol, EDB and I,2-DCA were not detected above laboratory reporting limits. — Analytical results of the soil samples are summarized in Tables 3 and 4; analytical results of the ground water sample are summarized in Table 5. 5.0. HYDROCARBONS REMAINING IN SOIL, The vertical and lateral extent of impacted soil is defined. Based on the concentrations of MTBE remaining in the soil. the MTBE plume is mapped as a vertically elongated cylinder of approximately 15 feet radius and 30 feet length (Figure 4). AGE calculated that an estimated 0.57 Egg or 1.25 lbs of MTBE remain in soil. The assumptions for the calculation of hydrocarbon mass remaining in soil is presented in Appendix C. 6.0. SOIL VAPOR EXTRACTION WELL INSTALLATION AND PILOT TEST One soil vapor extraction (SVE) well was installed and an SVE feasibility pilot test was conducted in .March 2002 to determining if remediation of the MTBE-impacted soil was necessary. Advanced GeoEavirolnuenlal,Inc.