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h } 17 February 2004 AGE-NC Project No 96-0254 Page 3 of 10 2 4 UNDER GROUND STORAGE TANK REMOVAL AND OVER-EXCAVATION ' On 10 September 1998, four USTs, including two 3,000-gallon gasoline USTs, one 4,000-gallon gasoline UST and one 12,000-gallon diesel UST,and two dispenser islands and associated product lines were removed from the site These tanks were in operation at the site for approximately twenty years The former UST locations are depicted on Figure 2 During the removal of the USTs and fueling system,AGE performed interim soil remediation when approximately 350 cubic yards of soil were removed from two UST excavations and four dispenser excavations On 15 September 1998,the interim soil remediation included removal of an additional 100 cubic yards of significantly diesel-impacted soil, from the bottom of the diesel UST excavation Soil was excavated from the diesel UST excavation at the central area of the site to a depth of 20 feet ' surface grade(bsg) One grab water sample was collected from the northern edge of the diesel UST over-excavation The soil left in place was impacted by low to moderate concentrations of total petroleum hydrocarbons as diesel (TPH-d) ' The analytical data indicated a significant concentration of diesel dissolved in the ground water Results of the September 1998 investigation were reported in Preliminary Investigation and ' Evaluation Report (PIER), dated 09 March 1999, prepared by AGE Analytical results of the soil samples collected are presented in Table 2, The analytical result of the grab ground water sample r collected is presented in Table 3 3.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUND WATER On 03 December 1998, six soil probe bonngs (B 1 through B6) were advanced at the site to assess OKI the lateral and vertical extent of petrolcum-impacted soil and ground water (Figure 2) TPH-d, �1 t*s benzene,toluene,ethylbenzene and xylenes(BTEX)and oxygenated fuel additives were not detected in any of the soil boring samples analyzed TPH-d and BTEX compounds were not detected in the & two water samples analyzed from boring B 1 and B6,but the oxygenated fuel additive methyl-tertiary 01�1 b°4, „l butyl ether (MTBE) was detected in both water samples analyzed at concentrations as high as "l�r� 760 micrograms per liter(µg/1) No other fuel additives were detected in the analysis of the water samples Analytical results of soil samples are presented in Table 2 Analytical results of the grab `r ground water samples collected during the December 1998 investigation are presented in Table 3 a,41 d On 12 and 13 January 2000, Monitoring wells MW-1, MW-2,MW-3 and MW-4 were installed at ' the site Total petroleum hydrocarbons as gasoline (TPH-g), TPH-d and BTEX were not detected above laboratory reporting limits in the nine soil samples analyzed from wells MW-1, MW-2 and MW-3 However, MTBE was detected in eight of the nine soil samples at concentrations ranging from 110 micrograms per kilogram (µg/kg) to 2,580 µg/kg (MW1-20) Analytical results of soil . samples collected from the January 2000 well installations are presented in Table 2 Advanced GwEnviron mental,Inc