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t 19 July 2005 AGE-NC Project No. 95-0135 ' Page 3 of 9 • Impacted soil encountered in the former UST cluster may extend,at depth,to the MW-1 area, but the lower hydrocarbon concentrations in the former UST cluster suggest otherwise.No soil contamination was encountered in boring B2, which extended only to 35 feet bsg. On 12 and 13 November 2002, three cone penetrometer test (CPT) borings (CPT-1, CPT-3 and CPT-4)were advanced on-and off-site(Figure 2)utilizing CPT technology.At each boring location, lithologic data was collected from the initial CPT boring;an immediately adjacent twin boring was then advanced to collect grab ground water samples from selected depths. In addition, although a CPT was not acquired, the EHD requested a soil boring at location CPT-2 for collection of grab Lim ground water samples. From this investigation, four vertical zones were identified: • Vadose Zone-Extending from surface grade to approximately 25 feet bsg,the depth to the water table. The vadose zone is predominantly fine grained material from surface grade to 25 feet bsg,with a coarse grain sand unit occurring between 25 feet and 30 feet bsg at CPT3 off-site. Hydrological Unit 1 (HU 1), at the top of the current saturated zone,extends from 25 feet to • approximately 45 feet bsg and is comprised predominantly of clay, interbedded on the southwest and on the northeast with clayey silt and silt. • Hydrological Unit 2 (HU2) extends from 45 feet to approximately 90 feet bsg and is composed dominantly of stiff, fine-grained soil, clayey silt, silt and lesser amounts of clay. • Hydrological Unit 3 (HU3) extends from 90 feet bsg to total depth; HU3 is composed of interbedded stiff,fine-grained soil, silty and gravelly sand,clayey silt and silty clay from 90 feet bsg to approximately 110 feet bsg and sand, silty sand and gravelly sand from 110 feet bsg to total depth. A total of eleven grab ground water samples and two soil samples were collected from HU2 and 1"r HU3 and submitted for laboratory analysis: TPH-g was detected in grab ground water samples collected from HU2 and HU3. The highest concentrations of TPH-g were detected at the base of HU2 at approximately 80 feet bsg. The lateral distribution of TPH-g suggests the possibility of additional source(s) of contamination. + BTEX compounds except ethylbenzene were detected in grab ground water samples from HU2 and HU3. Benzene was the most prevalent of the BTEX compounds, and is present at concentrations exceeding the DHS'Maximum Contaminant Level(MCL)for drinking water; in addition, the concentrations of benzene appear to increase with depth both on-site at CPT-1 and off-site at CPT-3 and CPT-4. The lateral distribution of benzene suggests the possibility of additional source(s) of contamination. Advanced GeoEnvironmental,Inc. �r