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2.05.4(2)(e) <br />The DMG has indicated that GVB's must be sealed with a continuous pour of <br />cement slurry from a minimum of 50 feet below the top of the perforated casing <br />to a minimum of 50 feet above the bottom of the blank casing. <br />Methane flow must be controlled before internal cementing is initiated, and the <br />open fissures created by caving of the gob must be sealed off or bridged over <br />to create a foundation for the cement to fill the column of drill hole and casing. <br />These two requirements will be accomplished by placing a plastic or paper plug <br />into the hole immediately following un-capping of the hole. A slurry gravel (3/4" <br />minus or smaller) and water will then be dumped into the hole in an appropriate <br />volume to occupy a 50 ft. column of hole and casing. Additional 50 ft. lifts of <br />gravel interspersed with paper or plastic plugs will continue until the flow of gas <br />has essentially stopped. When gas flow has discontinued, then a sounding <br />device will be lowered down the hole to determine exact depth to top of gravel. <br />A rubber tube packer may also be used to stop gas flow. The technique to <br />control methane flow is untested so alternative methods may be developed. <br />The perforated casing and a portion of the blank casing may be damaged by <br />the fracture zone above the longwall panel. The casing could be deflected, <br />crushed or sheared off. The extent of casing damage will determine the <br />sealing method. It the top 50 feet of the perforated casing is in tact and <br />methane flow can be controlled, a continuous pour of cement slurry will be <br />placed from 50 feet below the top of the perforated casing to the top of the <br />blank casing. If the perforated casing is not in tact, then a cement slurry will be <br />placed in the blank casing from the lowest point possible, with consideration of <br />methane control, to the top of the blank casing. The cement will be pumped <br />into the casing through a tremmie line. <br />u <br />TR-23 <br />2.05 - 58i - 6/02 <br />A P PRovED <br />6/a5/o Z <br />