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To prevent cross contamination during drilling and sampling operations, all equipment will be steam-cleaned or washed with laboratory-grade detergent, rinsed with tap water, and rinsed with deionized water before each use Groundwater Monitoring Well Construction Groundwater monitoring wells will be constructed using schedule 40, flush-threaded, blank and machine-slotted, polyvinyl chloride (PVC) casing. On-site monitoring wells will be completed with 4-inch-diameter PVC casing, while off-site wells will be completed with 2-inch-diameter PVC casing. The well perforations will be 0.020-inch machine-slots factory cut into the PVC casing. The slotted interval will extending from a depth of approximately 15 feet below the existing shallow groundwater table to approximately 10 feet above the existing water table. Blank PVC casing will extend from the top of the perforated section to the ground surface (or three-feet above ground surface, in the case of above-ground completion). The well design is intended to accommodate seasonal water-level fluctuations within the slotted interval. The well design may be modified in the field during the drilling operation, depending upon conditions encountered during drilling. In no case will the monitoring well penetrate clay zones existing beneath the shallow groundwater surface which have been identified as being greater than 5 feet thick. Penetration of such zones might allow downward migration of contaminants into lower water-bearing zones. A flush-threaded PVC cap will be installed at the bottom of each well. The annular space surrounding the slotted interval and casing will be packed with Lonestar No. 3 (or equivalent) silica sand (unless otherwise noted in the work plan), from the bottom of the slotted interval to approximately 2 feet above the top of the slots. The well will then be surged to settle the filter pack and additional sand will be added as necessary to return the level to a height of 2 feet above the top of the slots. A 2-foot-thick seal of bentonite pellets or chips will be placed above the sand pack and hydrated using tap water. The annulus will then be backfilled with a bentonite-cement slurry containing approximately 5-percent powdered bentonite, or neat cement, from the top of the bentonite seal to just below the ground surface. The top of the well casing will be sealed using a locking, water-tight, cap. Groundwater monitoring wells will be completed at grade using a flush-mounted, traffic-rated, water-tight containment box set in concrete, or above grade using steel well monuments set in concrete. The horizontal location and top of casing (TOC) elevation will be surveyed by a licensed surveyor, and all depths to water will be measured in relation to the surveyed mark on the TOC. Groundwater Monitoring Well Development Prior to development, the well cap will be removed from the top of the casing and the water within the well will be allowed to come to equilibrium with atmospheric pressure. The depth-to- E:'2092\ph=ffiworkple do