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ME <br /> Al <br /> a <br /> testing is mandated for all ground water monitoring wells <br /> installed within 50 feet of a sanitary sewer. A summary of <br /> the results of the water sample analyses is presented in <br /> Tabu 5. The official laboratory reports and chain of <br /> custody documents are included in Appendix B. <br /> 3.3 Site gzgglagy andydroueo12gv <br /> The area of excavation has been backfilled with sandy gravel <br /> to a depth of approximately 10 feet below grade. A review of <br /> " the boring logs shows that with the exception of the <br /> backfilled area, the predominant soil type at the site is <br /> sandy silt from ground surface to a depth greater than <br /> 11 feet. Sandy silt may persist to nearly 15 feet below <br /> grade. . In Boring B-2, sandy silt was encountered in the <br /> " sample collected from a depth of 15 feet. Only in the sample <br /> from a depth of 15 feet in Boring B-3 was sand noted; sand <br /> was not observed .in any other sample retrieved during <br /> drilling. A stiff to hard silty clay unit underlies the sand <br /> and sandy silt unit, persisting to the total depth of the <br /> borings (approximately 25 feet below grade) . <br /> Ground water was firs encountered during drilling at <br /> approximately 10 feet below grade in all soil borings, <br /> stabilizing at an average depth of about 11.5 feet below the <br /> top of casing. The ground water elevation data from <br /> October 1, 1990, was used to develop the ground water <br /> elevation contour map shown as Figure 6. The data indicates <br /> that shallow ground water at the site flows in a <br /> north/northwesterly direction, with a calculated average <br /> hydraulic gradient of 0.004 foot per foot. <br /> a 3.4 Discus,s,ion of Results <br /> Four soil borings were drilled to depths of 25 feet below <br /> -' grade each. These borings were subsequently completed as <br /> ground water monitoring wells. Ground water is present at an <br /> average depth of 11.5 feet below top of casing. No TPH-G, . <br /> TPH--D, BTEX, or organic lead were'd tected above method <br /> detection limits in any of the soil samples collected ..from <br /> 3 � t e fair horings. <br /> Ground water samples collected from the wells were analyzed <br /> for TPH-G, TPH-D, BTEX, organic lead,. and fecal coliform <br /> (AW-1 and AW-3) All constituents were not. detected above <br /> method detection- limits in all samples except from AW-3 <br /> which had detectable concentrations of TPH-D, TPH--G, and <br /> BTEX. The levels of all BTEX detected in the sample from.. <br /> AW-3, however, were all below the state primary maximum <br /> contaminant levels (MCL) for drinking water. <br /> 9 <br />