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07 February 2001
<br /> AGE-NC Project No 95-0130
<br /> ' Page 5 of 8
<br /> monitoring well ground water samples collected on 31 October 2000 are depicted in cross sectional
<br /> ' views C-C'and D-D'(Figures 5 and 6)
<br /> ' 3 0. SUMMARY AND CONCLUSIONS
<br /> ' The implications of the December 2000 CPT investigation results are as follows
<br /> • Permeable lithology consisting of gravel, fine to coarse sand was observed at depths between
<br /> ' 25 and 45 feet bsg, 70 and 75 feet bsg, 82 and 90 feet bsg and 130 and 150 feet bsg
<br /> Conversely, less-permeable fine grained, silty clay and clayey silt was observed at depths
<br /> between 10 and 25 feet bsg, 50 and 60 feet bsg, 90 and 105 feet bsg and between 115 feet
<br /> and 125 feet bsg Variable lithology including silty fine sand and sandy silt was observed at
<br /> all other depths AGE interprets the CPT data to identify four potential hydrogeologic units
<br /> informally identified as "First Water Zone" (located 15 to 47 feet bsg), "Second Water
<br /> Zone" (located 58 to 92 feet bsg), "Third Water Zone' (located 102 to 115 feet bsg) and
<br /> Primary Aquifer Zone"(located 128 to 150 feet bsg) It is not known how effectively the
<br /> • intervening fine grained intervals hydrologically separate the informal hydrogeologic units
<br /> though some contamination has migrated through or around there Geologic cross sections
<br /> C-C'and D-D were generated from CPT data collected at P-7, P-8, P-9 and P-10 and depict
<br /> general lithology beneath the site in cross sectional view (Figures 3 and 4, respectively)
<br /> • Dissolved constituents of concern detected at P-7, P-8, P-9 and P-10 were TPH-g, TPH-d,
<br /> BTEX, MTBE, PCE, TCE, 1,2-DCE, TAME has previously been detected in ground water
<br /> ' samples collected at MW-1
<br /> • Generally, the greatest hydrocarbon and solvent-impact was reported from grab w ater
<br /> samples collected at P-8, TPH-g, TPH-d, BTEX, MTBE, PCE, TCE and 1,2-DCE were
<br /> detected at various depths between 43 and 132 feet bsg With depth, the MTBE and BTEX
<br /> concentrations decreased, however, concentrations of TPH-g, TPH-d, PCE, TCE and 1,2-
<br /> DCE were variable with depth The greatest TPH-g-impact was detected at depths between
<br /> 50 to 53 feet bsg and 112 to 115 feet bsg , however, the laboratory reported the TPH-g and
<br /> TPH-d sample chromatograms from P-8 as having substantial peaks of chlorinated
<br /> hydrocarbons The greatest PCE-impact was detected between 112 to 115 feet bsg and 134
<br /> to 137 feet bsg, TCE and 1,2-DCE were detected in samples collected between 50 and 53
<br /> feet bsg Constituents of concern detected at P-8 are depicted by informal hydrogeologic
<br /> ' units in cross sectional views (-C and D-D (Figures 5 and 6)
<br /> • Vanable concentrations of TPH-g,MTBE, PCE, TCE and 1,2-DCE were reported from P-7
<br /> ' at various depths between 43 and 137 feet bsg TPH-g was detected in three consecutive grah
<br /> water samples at depths between 73 to 76 feet bsg, 101 to 104 feet bsg and 129 to 132 feet
<br /> bsg, however the laboratory reported that the TPH-g chromatograms from P-7 as having
<br /> ' Advanced 6coEnvironmenlal Int
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