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1 <br /> 1 <br />' 27 October 2004 <br /> • AGE-NC Project No 96-0254 <br /> ' Page 4 of 10 <br /> On 11 December 2000, ground water monitoring wells MW-5 and MW-6 were installed on-site to <br /> 1 assess the lateral extent of MTBE-impacted ground water Soil samples were not collected during <br /> the well installations <br /> ' On 20 December 2000,ground water extraction well EW-1 was installed at the site for performance <br /> of a ground water pumping test The soil boring EW-1 was advanced vertically to a depth of 30 feet <br /> bsg Boring EW-1 was single-completed as a�lnch diameter ground water extraction well,screened <br /> 1 between 15 and 30 feet bsg Soil and ground water samples were not collected during this <br /> investigation <br /> ' The initial monitoring and sampling of wells MW-5 and MW-6 and extraction well EW-1 occurred <br /> on 29 March 2001 Laboratory analysis did not detect TPH-d and BTEX compounds in the ground <br /> 1 water samples, but MTBE was detected in samples MW-5 and EW-1 at concentrations of 16 µg/l <br /> and 2,200 gg/l, respectively, MTBE was not detected in sample MW-6 <br /> ' On 01 November 2002, ground water monitoring wells MW-7 and MW-8 were installed off-site to <br /> further assess the lateral extent of MTBE-impacted ground water Soil samples were not collected <br /> during the well installations •- <br /> 1 • <br /> ' 3 0. SOIL PROPERTIES <br /> Silty sand was encountered from surface grade to approximately 30 feet west and east of the former <br /> diesel UST, while silty sand and interbedded silty clay was encountered south and north of the <br /> 1 former diesel UST from depths of 15 to 30 feet bsg A clay to clayey silt layer was encountered at <br /> the base of the former diesel UST area from a depth of 20 to 25 feet bsg A sand layer was <br /> ' encountered south of the UST at a depth of 20 feet and under the UST at a depth of 25 feet bsg Silt <br /> and coarse sand were encountered from a depth of 30 feet to 45 feet bsg,while clay or silty clay was <br /> observed in deep borings B7 to B9 from 45 to 50 feet bsg Monitonngwell logs,soil boring logs and <br /> 1 construction specifications are presented in Appendix A Stratigraphic cross sections are depicted <br /> on Figure 4 el <br /> ' 4.0. PETROLEUM HYDROCARBON DISTRIBUTION IN SOIL <br /> ' Based on low concentrations of TPH-d in soil satiaples collected during the UST removal and <br /> over-excavation and the concentrations of MTBE detected in soil samples collected from the water <br /> bearing zone,AGE believes soil remediation is unnecessary due to the affinity of MTBE to dissolve <br /> 1 and migrate in ground water and due to the lack of adsorbed contamination above the current and <br /> past water table depths (Figure 6) <br /> ' Advanced CcoEnvironmental,Inc <br /> 1 <br />