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chemical composition of the soil and groundwater <br /> Drilling Methods: Acceptable drilling methods include solid and <br />' hollow--stem auger, percussion, direct circulation mud and air <br /> rotary, and reverse rotary. The best alternative is that which <br /> minimizes the introduction of foreign materials or fluids. If <br /> drilling fluid is employed, drilling fluid additives shall be <br /> limited to inorganic and non-hazardous compounds. Compressed air <br /> introduced into the borehole shall be adequately filtered to <br /> remove oil and particulates. <br /> 1 Casing Installation: The casing will be set under tension, when <br /> necessary, to ensure straightness. Centralizers will be used <br />' where necessary to prevent curvature or stress to the casing. <br /> Sand Pack Installation: The sand pack will be installed so as to <br />' avoid bridging and the creation of void spaces . The tremae pipe <br /> method will be used where installation conditions or local <br /> regulations require . Drilling mud, when used, will be thinned <br /> prior to pack placement. The sand pack shall cover the entire <br />' screened interval and rise a minimum of 2 feet above the highest <br /> perforation <br />' Bentonite Seal Placement A bentonite seal will be placed above <br /> the sand pack by a method that prevents bridging. Bentonite <br /> pellets can be placed by free fall if proper sinking through <br /> annular water can be assured Bentonite slurry will be placed by <br /> the tremae pipe method from the bottom upward . The bentonite <br /> seal will not be less than 1 foot in thickness. <br />' Grout Seal Placement : The cement grout mixture will be hydrated <br /> with clean water and thoroughly mixed prior to placement. If <br /> substantial groundwater exists in the bore hole, the grout shall <br />' be placed by tremae pipe method from the bottom upward. In a dry <br /> borehole, the grout may be surface poured to a depth of 30 feet. <br /> Below a depth of 30 feet grout will be placed by tremae pipe. <br /> Grout will be placed in 1 continuous lift and will extend to the <br />' surface or to the well vault if the well head is completed below <br /> grade. A minimum of 5 feet of grout seal will be installed, <br /> unless impractical due to the shallow nature of the well . <br />' Surface Com letion The well head will be protected from fluid <br /> entry, accidental damage, unauthorized access, and vandalism. A <br /> watertight, locking cap will be installed on the well casing. <br /> Access to the casing will be controlled by a keyed lock. <br /> Well head, completed below grade will be completed in a concrete <br /> and/or steel vault, installed to drain surface runoff away from <br /> the vault. <br /> Well Identification: Each well will be labeled to show well <br /> number, depth, hole and casing diameter, and screened interval . <br /> I <br />