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19 June 2001 AGE-NC Project No 97-0326 Page 4of7 units,are interpreted as potentially effective groundwater flow units HSU-I,which is a fine grained ' interval,is considered to be a leaky confining layer because the water table lies at approximately 30 feet bsg within this unit, and the highest levels of contaminates in ground water samples were assessed from this interval Similarly the third fine-grained HSU is also considered to be a leaky ' confining layer because water and contaminants have apparently migrated through or around it Geologic cross sections A-A ' and B-B' were generated from the CPT data and depict general lithology beneath the site in cross sectional view (Figures 3 and 4, respectively) ' Copies of the computer-generated CPT boring logs are included in Appendix A 3 2 LABORATORY RESULTS OF GRAB GROUND WATER AND SOIL SAMPLES A total of eleven grab ground water samples and two soil samples were collected from CPT-01, CPT-02 and CPT-03 and submitted for laboratory analysis for the constituents Iisted in Section 2 2 ' No petroleum hydrocarbon compounds were detected in the two soil samples analyzed(see Table 1} For the ground water samples the analytical results from each HSU are HSU-1 TPH-g and BTEX compounds were assessed in all ground water samples collected from HSU-1, which had the highest concentrations of TPH-g and BTEX compounds detected in the water samples collected Analysis of a ground water sample collected at the top of HSUA (at the water table, 30 ' to 40 feet bsg)from off-site CPT-03 detected 110µg/1 TPH-g,2 1 µg/1 benzene,3 8µg/1 toluene and 0 53 µg11 xylenes,respectively The maximum concentrations ofpetroleum hydrocarbon compounds (4,900 µg/I TPH-g, 710 µg/1 benzene and 82 µg/1 ethylbenzene) were detected in off-site CPT-03, ' in a sample collected between 55 and 70 feet bsg In addition to TPH-g and the BTEX compounds, low concentrations of di-isopropyl ether(DIPE), ' isopropylbenzene, n-propyl benzene, 1,1,2-trichloroethane, 1,2-dichloroethane, 1,2,4- tnmethylbenzene and 1,3,5-tnmethylbenzene were also detected in HSU-1 Isopropylbenzene was ' detected at all CPT locations,n-propyl benzene and 1,1,2-trichloroethane were detected in samples from CPT-01 and CPT-03, 1,2,4-and 1,3,5-tnmethylbenzene were detected only in the sample from CPT-01, and DIPE and 1,2-dichloroethane were only detected in the sample from CPT-02 The higher concentrations of isopropylbenzene (22 µg/1), n-propyl benzene (74 µg/1) and 1,1,2- trichloroethane (30 µg/1) were detected in the sample from off-site boring CPT-03 Advanced GeoEnvironmental,Inc