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Wells Through the Concrete Slab <br /> E� The proposed preliminary well locations for the three wells to be drilled <br /> through and screened beneath the slab are shown on Plate 2. Boring data from <br /> Kennedy/Jenks/Chilton's October 1986 study will be used to guide placement of <br /> the wells. The well completions will be logged and developed in accordance with <br /> 6� the procedures discussed previously with several following additions. It is <br /> important to isolate any hydrocarbons present above the slab from the zone <br /> beneath the slab. We would therefore include the following additional proce- <br /> dures for the three wells only: <br /> o A 16-inch diameter hole - will be drilled to the top of the concrete <br /> slab; <br /> o The hole will be cleaned out thoroughly of cuttings using an industrial <br /> vacuum cleaner or the equivalent; <br /> o A 12-inch diameter steel casing extending from the concrete slab to the <br /> ground surface will be emplaced in the borehole. The vacuum equipment <br /> will again be used to assure that the inside and outside of the casing <br /> are free of cuttings; <br /> o The outside of the casing will be grouted with a 2% bentonite/cement <br /> mixture; <br /> o The grout will be allowed to set overnight. The hole will be inspected <br /> prior to continued drilling to confirm that the grout seal is effec- <br /> tively preventing inflow of any ponded hydrocarbons; <br /> o A 10-inch diameter hole will be advanced inside the steel casing; <br /> o After drilling to the desired depth the hole will again be cleaned at <br /> the slab using the vacuum to ensure that the exposed concrete is as <br /> Fclean as possible for grout bonding; <br /> o Install and develop the wells as described previously. <br /> After installation and development of these wells the presence and thickness <br /> P <br /> of free oil on the water table will be measured using an interface probe. These <br /> JED2/H -10- <br />