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l <br /> the proposed screened interval using a . 15 1/2-inch diameter drag bit and <br /> conventional fluid rotary methods. A 10 3/4 diameter steel casing will <br /> then be set from the surface to the bottom of the borehole and pressure- <br /> cemented in place. After allowing the cement to cure, the borehole will be <br /> drilled to its total depth and 4-inch flush-threaded PVC casing will be <br /> installed from the surface to the bottom of the borehole, with slotted <br /> casing over the appropriate interval. Since volatile organics are not the <br /> contaminants of concern and groundwater samples will only be analyzed for <br /> total chromium and hexavalent chromium, PVC casings will be suitable for <br /> C <br /> the proposed wells -.and will not interfere with the analyses of the <br /> groundwater samples.; The casing will be sand-packed from the total depth <br /> to approximatel .�2 meet above ,the top of the slotted casing. A bentonite <br /> seal will be plaaced�on to czf the sand pacts and the remaining annular space <br /> e <br /> �,ti R� �s pa <br /> will be filled with -pry--gravel to within 20 feet of the land surface. me <br /> annulus will be sealed with cement over the remaining distance to the lacid <br /> surface. A subgrade utility vault will be set around the conductor casing <br /> and cemented in place. A locking steel well housing will also be installed <br /> within the utility vault. Each well will be equipped with a dedicate-d <br /> submersible pump to facilitate sampling. <br /> F <br /> Following well development and water level drawdown and recover] <br /> m aau wamesits, amach of the naw wells will be sampled. Zciating wnitoring <br /> wells will also be sample, if the location and the depth of the screeried <br /> r interval in specific existing wells are such that sampling these wells will <br /> help to define the contaminant plume. In addition, the one operational <br /> private groundwater well downgradient of the MCTC facility identified in <br /> the Off-site Residential Well Summary will be sampled. <br /> Wells will be purged until temperature, conductivity, and ph have <br /> stabilized, as indicated by variation of less than 10 percent for 3 <br /> successive measurements of 2 of the 3 parameters, before samples are <br /> collected. Samples will be collected at the wellhead and placed in 1;2 <br /> liter wide-mouth plastic bottles. Tree samples will be filtered and <br /> preserved with acid for total chromium at the laboratory within 24 Hours. <br /> Duplicate sample:: will be collected for a minimum of 10 percent of the <br /> 4--9 <br /> t <br />