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U-Haul##709-50 Blaes Envtrotimetttal ' Additional Site Charactenzation ' occurring at the site One additional nested groundwater well was installed on the southern portion of the site to further evaluate the extent of hydrocarbons in that direction 3 3 1 Groundwater Well Installation Blaes Environmental contracted a licensed drilling contractor, Gregg Drilling, to install eight groundwater monitor wells As mentioned above, seven of the proposed monitor wells will accompany the existing on- site monitor wells and one additional well was installed on the southern portion of the site (Figure 4) One additional well (MW-8a) was constructed with a single 4-inch diameter casing, screened between approximately 37 to 62 feet bgs The other new wells were constructed with two, 2-inch diameter nested well casings The wells were designed to account for recent fluctuations in groundwater levels that have ranged from 66 feet bgs in February 1995 to 37 feet bgs in March 1999 The existing and proposed well casing screen intervals are presented on Table 3 Well installation activities complied with regulatory 1 requirements and the regulatory well permits issued for each well With exception to monitor well locations MW-3ab and MW-gab,the new wells were installed within 10 feet of the existing monitor wells Monitor well MW-3ab was installed near the release area, near DP-2 and B-7 (Figure 4), to determine if free-phase hydrocarbons were present on groundwater The pre-existing location of MW-3 was not close enough to the release area to monitor source area concentrations Monitoring well MW-9ab was installed on the south side of the site to monitor the southern extent of dissolved-phase hydrocarbons This well location was chosen based on the analytical results of the ' groundwater sample collected at hydro-punch location HP-1 ' 3 3 2 Qroundwater Well Development Upon installation of the casing and filter pack at each well, the drilling contractor developed the wells by surging and bailing Using the drill ng, a decontaminated surge tool was lowered and raised multiple times across the screened interval of the well to surge the well Surging the filter pack of the well ensured that the filter pack settled properly Bailing followed surging to remove the sediment pulled into the well during surging Surging and bailing continued until the bailed water contained little or no sediment Due to the limited amount of water to the upper casing of the nested wells, only the lower casing was surged and bailed Approximately 25 gallons of groundwater was bailed from each well and stored in four, 55-gallon drums The drums were properly labeled and stored on-site pending waste profiling and removal lI