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t25 October 2005 <br /> . AGE-NC Project No 02-0926 <br /> ' Page 5 of 7 <br /> i <br /> uniformly low <br /> ' HU3 - HU3 extends from 70 feet to approximately 73 feet bsg and consists of sand, silty sand, and <br /> pP Y g tY <br /> sandy slit with low pore pressures This unit may be considered a flow unit <br /> 1 <br /> HU4 - HU4 extends from 73 feet bsg to between 80 feet and 82 feet bsg, and consists primarily of <br /> clayey silt,silt,and stiff,fine-grained material Pore pressures within this unit are moderate to high <br /> HU5 - Extending from between 80 feet and 82 feet bsg to approximately 90 feet bsg, this unit <br /> ' consists primarily of interbedded silty and clayey material Pore pressures range from low to <br /> moderately high, local zones of low pore pressure appear to be due to the presence of discontmous <br /> lenses of sandy material <br /> HU6 -Extending from approximately 90 feet bsg to the total depth of the borings, HU6 consists of <br /> interbedded silty, clayey, and stiff, fine-grained material This unit is characterized by low to <br /> ' moderately high pore pressures <br /> The model presented is interpretational and may be modified as additional data is collected <br /> 3 3 ANALYTICAL RESULTS OF GRAB GROUND WATER SAMPLES <br /> A total of six grab ground water samples were collected and analyzed for the petroleum hydrocarbon <br /> constituents listed in Section 2 2 ,the analytical results are listed according to the hydrogeologic unit <br /> ' in which the samples were collected (Table 2) <br /> ' HU3 <br /> TPH-g was detected in ground water sample CPT3-68-72 at a concentration of 160 micrograms per <br /> ' liter(µg11) BTEX compounds were detected in sample CPT3-68-72 at the following concentrations <br /> 7 2 µg11 benzene, 6 7 gg/l toluene, and 9 0 µg11 total xylenes <br /> ' HU4 <br /> Benzene was detected at a concentration of 4 7 gg/1 in sample CPT3-87-90 <br /> ' No additional petroleum hydrocarbons were detected at or above laboratory reporting limits in any <br /> of the grab ground water samples analyzed A cross section depicting the estimated vertical <br /> ' distribution of dissolved petroleum hydrocarbon contamination is illustrated on Figure 3 The <br /> laboratory report(CTEL Project No CT214-0508166), quality assurance/quality control(QA/QC) <br /> ' Advanced GeoEnvironmental,Inc <br />