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AGE-NC Project No. 99-0559 <br />Page 9 of 13 <br />HU5 Upper <br />Samples CPT4-120, CPT5-130, CPT6-125, CPT7-130 and CPT8-125 were collected from <br />Upper HU5. TPH-g was detected only in sample CPT6-125 at 190 pg/I, and the fuel <br />additive MTBE was detected in samples CPT4-120, CPT6-125 and CPT8-130 at a <br />maximum concentration of 91 pg/I (CPT6-125). No other analytes were detected in the <br />Upper HU5 samples. <br />HU5 Lower <br />Samples CPT5-150, CPT6-150, CPT7-150 and CPT8-165 were collected from Lower HU5. <br />The fuel additive TBA was the only analyte detected in the Lower HU5 samples, at a <br />concentration of 180 pg/I. <br />TPH-g was detected is groundwater samples collected in HU2, HU4 and Upper <br />HU5; the maximum concentration was 2,000 pg/I in HU4. BTEX compounds were <br />detected only in HU2. <br />Fuel additives were detected in all hydrologic units. The highest concentrations were <br />detected in HU4; MTBE was detected in HU4 at a maximum concentration of 2,600 <br />pg/I, ETBE and TAME were detected at 25 pg/I and 5.6 pg/I, respectively, and TBA <br />and DIPE were detected at 630 pg/I and 18 pg/I, respectively. However, only TBA <br />was present in Lower HU5, at a concentration of 180 pg/I. HU4 is a thick poorly <br />graded sand layer encountered at approximately 90 to 110 feet bsg. MTBE is <br />apparently migrated laterally within this unit, especially off-site towards the west. <br />Dissolved MTBE extends off-site past all current sampled locations. The <br />concentrations of dissolved MTBE decreased away from the site, except to the west <br />at CPT4, the highest concentration of MTBE detected off-site. <br />The vertical extent of dissolved TPH-g, benzene and MTBE does not extend to <br />below 130 feet bsg. <br />The solvent TCE was detected in HU2 and HU4 in the off-site borings CPT-5 and <br />CPT-8 (Figure 2), at a maximum concentration of 1,700 pg/I. The TCE appears to <br />originate from an off-site source, since TCE was not detected in CPT borings (e.g., <br />CPT-4 and CPT-6) closer to the site. <br />Computer generated CPT soil descriptions augmented with previously obtained soil sample <br />and CPT soil descriptions were utilized to construct the vertical and lateral geologic model; <br />laboratory analysis of groundwater samples was utilized to assess the hydrocarbon-impact <br />on the dissolved media. <br />Advanced GeoEnvironmental, Inc.