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i • <br /> Former Unocal Station No 0187 <br /> February 14, 1995 <br /> cleaning ansate waste water will be stored on site in properly labelled drums <br /> pending disposal <br /> 2 Vapor Extraction Wells <br /> Depending on field screening data from the collected soil samples and observed <br /> subsurface conditions, a vapor extraction well may be installed In any or all of <br /> the onsite soil bonngs (U-N, U-O, or U-P) If vapor extraction wells are to be <br /> installed, the chosen boring(s) will be reamed with 12-inch-diameter augers The <br /> vapor extraction wells will be constructed of four-inch-diameter Schedule 40 <br /> polyvinyl chloride (PVC) well casing and 0 05-inch machine-slotted well screen <br /> Based on data obtained during previous subsurface investigations at the site, we <br /> anticipate the screened interval in each vapor extraction well would extend from <br /> approximately 15 to 45 feet bgs Construction details for the proposed vapor <br /> extraction wells are presented on Figure 4 <br /> 3 Groundwater Monilgnng Wells <br /> Install three onsite groundwater monxtonng wells (U-4, U-5, and U-6) at the <br /> locations shown on the Site Plan (Figure 2) and two offsite groundwater <br /> monitoring wells (U-7 and U-8) at the locations shown on the extended Site Plan <br /> (Figure 3) The wells will be installed in soil borings drilled with eight-Inch- <br /> diameter hollow-stem augers A GSI geologist will monitor the drilling activities <br /> and prepare a log of each boring A groundwater monitoring well will be <br /> constructed in each boring using two-inch-diameter Schedule 40 PVC well casing <br /> and 0 02-inch machine-slotted well screen Based on data obtained during <br /> previous subsurface investigations at the site, we anticipate the screen interval <br /> in each well will extend from approximately 35 to 55 feet bgs Construction <br /> details for the proposed groundwater monitoring wells are presented on Figure <br /> 5 <br /> Soil samples for description and possible chemical analysis will be obtained from <br /> the borings at five-foot intervals, as a minimum Soil samples will be collected <br /> and screened as described above in Task 3 1 We anticipate three samples- <br /> well boon will be submitted for chemical analysis Drill cuttings and cleaning <br /> rinsate water will be an as escn e a ove in Task 3 1 <br /> 3.4 Wellhead Survey_ <br /> Following installation of all groundwater monitoring and vapor extraction wells, <br /> the elevations of the well vault boxes and tops of the well casings will be <br /> 4827 04-1 6 <br /> GeoStrategies Ince <br />