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into the center of the drill core (2-inches in diameter) Each soil sample was lined with Teflon TM sheets, capped, and sealed Each sample was labeled, placed in a resealable plastic bag, and stored in an ice-chilled cooler Select soil samples were forwarded to a state certified analytical laboratory for cheaucal analysis Strict choAn-of-custody procedures were followed from the time the samples were collected until the time the samples were relinquished to the laboratory Additional soil from each sampled interval was placed and sealed in plastic bags to allow the accumulation of volatile organic compound (VOC) vapors within the airspace in the bags A portable photo-ionization detector (PID) was used to measure VOC concentrations from each sample in parts per million by volume (ppmv) PID results are included on the boring logs presented in Appendix A Well Installation Stratus retained Woodward Drilling Company of Rio Vista, California (C57 #710079) to drill and install wells MW-10 through MW-15 using a truck mounted drill ng equipped with hollow stem augers Geologic and analytical data obtained from borings B-39 through B-42 were used to guide the screening intervals and locations of the wells installed during this phase of investigation Since each well was installed in close proximity to previously logged bonngs B-39, B-40, and B-42, soil samples were not collected from the well borings Due to minimal petroleum hydrocarbon impact observed at boring B-41 (discussed in section 4 of this document), no additional wells were installed in the immediate vicinity of boring B-41 Each well was constructed using 4-inch diameter PVC well casing and 0 02-inch diameter . factory slotted well screen Wells MW-10 and MW-15 were screened from approximately 84 to 109 feet bgs, well MW-11 was screened from approximately 83 to 108 feet bgs, well MW-12 was screened from approximately 90 to 105 feet bgs, well MW-13 was screened from approximately 58 to 68 feet bgs, and well MW-14 was screened from approximately 50 to 70 feet bgs A filter pack of Lonestarm #3 sand was placed in the annular space around the well, from the bottom of the casing to approximately 2 to 3 feet above the top of the well screen Approximately 2 to 3 feet of bentonite was placed on top of the filter pack and hydrated with clean water to provide a transition seal for the well The remaining annular space around the well casing was backfilled with neat cement up to surface grade A 12-inch diameter traffic rated vault box was placed over the wells, and a watertight locking cap was placed on the top of the well casing Well Destruction Woodward Drilling Company destroyed wells VW-15 and MW-11 by overdrilling with 10-inch diameter hollow stern augers To avoid potential wandering of the hollow stem augers away from the original borehole used to construct the wells, a "casing chaser" drill bit was attached to the lead hollow stem auger Following overdrilling of the wells to total depth, the drill bit was removed and the boreholes were backfilled to surface grade with neat cement The vault boxes covering each well were removed and the surface was finished with concrete P\Bp-Ar o for URS161005Reports\a�6100-�sessimnt sc�upiate 6o Page 5 5 MA 7-115