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1 ' significantly over a period of 3'/z years However, a mass/volume estimate of gasoline was not included in the report In a letter dated January 25, 1995 PHS/EHD stated that based on the results of the additional ' investigation performed by Hunter, residual soil contamination remained at unacceptable levels, and recommended a groundwater investigation be conducted to determine groundwater conditions ' and gradient MONITORING WELL INSTALLATION 1 On October 24 and 25, 1995, Ground Zero observed V & W Drilling drill three soil borings ' (SB1 through S133) at locations shown on the attached Site Plan (Figure 2) During drilling, soil samples were collected at five foot intervals for logging and analytical purposes Boring logs are included in Attachment B ' Soil borings SB1 through S133 were drilled to depths of 80, 80, and 75 feet bgs, respectively Groundwater was first encountered at approximately 65, 68, and 67 feet bgs, and subsequently ' rose to approximately 63, 62, and 59 feet bgs, respectively The onsite stratigraphy, based on borings S131 and SB2, consisted of lean clay and elastic silt to approximately 29 feet bgs, well to poorly graded sand and well graded gravel from approximately 29 to 43 feet bgs, lean clay ' and elastic silt from approximately 43 to 53 feet bgs, silty sand to poorly graded sand from approximately 53 to 70/73 feet bgs with a lens of elastic silt in boring SB2 from approximately 58 to 68 feet bgs, and lean clay from 70/73 to 80 feet bgs, the maximum depth explored The offsite stratigraphy, based on boring SB3, is similar to a depth of approximately 38 feet bgs where lean clay was encountered to approximately 48 feet bgs, poorly graded sand from 48 to 75 feet bgs with a lean clay lens from 63 to 69 feet bgs The only noticeable hydrocarbon odor was very slight at 25 feet in SB1 Borings SBI through SB3 were completed as monitoring wells MW1 through MW3, ' respectively The wells are constructed of 2-inch diameter PVC casing with 0 020 inch slotted screen installed from the bottom of each of the borings to approximately 55, 60, and 55 feet bgs, ' respectively The annulus was completed with #2/12 sand filter pack to 1 to 2 feet above the screened interval, overlain by a two foot thick plug of bentonite, and completed with a cement slurry to ground surface The wellheads were surveyed by Wong Engineers, Inc with an ' accuracy of 0 01 feet relative to mean sea level Wellhead survey information is included in Attachment C ' MONITORING WELL DEVELOPMENT AND GROUNDWATER SAMPLING The wells were developed on November 1, 1995 by Del-Tech Geotechnical Support Field ' reports are included in Attachment C The depth to bottom in each of the wells was significantly higher than when installed During development, the groundwater was turbid and had a high pH indicating a possible influx of cement grout into the well casing Wells MWI. and MW2 eventually cleared, but MW3 did not groundzelnormaclsumrepor 95 3