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21 January 2004 AGE-NC Project No. 95-0135 Page 3 of 7 not detected in sample B5-W. Analytical results of the soil and water samples collected during June 1999 are displayed in Table 3. On 27 and 28 September 2001, three soil borings were advanced at the site. Pilot borings MW-2, MW-3 and MW-4 were completed as ground water monitoring wells. Soil in the area of borings MW-2, MW-3 and MW-4 were not impacted by petroleum hydrocarbons or fuel oxygenating compounds.The lateral and vertical extent of impacted soil has been defined on the site.Analytical results of the soil samples collected during September 2001 are displayed in Table 4. Petroleum hydrocarbon-impacted ground water appears to be limited to the area near monitoring well MW-1.None of the target analytes were detected in samples collected from MW-2,MW-3,MW-4 and domestic well DW-1. Analytical results of the ground water samples collected are displayed in Tables 6 and 7. 2.4. SITE CONCEPTUAL MODEL Based on the data collected to date from soil borings and monitoring well installations, AGE has developed a site conceptual model for the release,migration and distribution of the contaminants in the subsurface as described below: The shallow stratigraphy is composed of an upper layer (Layer 1) of between 15 and 20 feet of yellowish to brownish green, generally unconsolidated, fine to medium sand, underlain by an approximately 15-foot thick clayey silt layer(Layer 2);northwards,Layer 2 appears to transition into a sandy silt or silty sand with clay, and beneath former USTs No. 1 and 2, a discontinuous lense of green to olive gray fine sand was identified near the top of Layer 2. The third layer (Layer 3), at below 35 feet bsg,appears to be an olive green to brown,unconsolidated coarse to pebbly sand;this layer was defined on the basis of the two deepest soil boringsTsecions and B-1)located at the former USTs' No. 1 and 2, respectively (Figure 2). Geologic cross are provided in Figures 3, 4 and 5. -Thee i s no,m u1'(. Releases of petroleum hydrocarbons occurred from the on-site USTs. Once released to the subsurface,the contaminants migrated through the sandy Layer 1 to a vertical depth of approximately 20 feet bsg, at which point the contaminants encountered the less porous clayey silt of Layer 2 and began to migrate laterally as well as vertically; the direction of lateral migration was dominantly towards the northwein the preferred ground water flow direction. J�+ice -Significant petroleum-hydrocarbon impac�tosoil in the vadose zone is present in time, a� B-4-20, MW-2-25 and MW-4- s, an, doff-site well MW-9-20 _ET-a. Me�j'`i�Fi-&PPH-d and TPH-mo are present at maximum concentrations of 670 m�/kg-(B--2- '4,o-+fi Advanced GeoEnvironmental,Inc. v' ) Q