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2.05.4(2)(e) <br /> certainty added to the plug length and will propose that a minimum plug length should <br /> be 3-feet, or 4 times that calculated. A sketch of the water tight seal is shown on <br /> Map-30 of Volume II. <br /> (2)(g) Drill holes, not completed to aquifers will be sealed by replacing cuttings or other <br /> suitable media in the hole and placing a suitable plug 10 feet below the ground to <br /> support a cement plug or other media approved by the Division to within 3 feet of the <br /> ground surface. <br /> Sealing of the drill holes will prevent acid or other toxic drainage for entering ground <br /> waters, minimize disturbance to the prevailing hydrologic balance and ensure the <br /> safety of people, livestock, fish and wildlife, and machinery in the permit and adjacent <br /> areas. <br /> Drill holes completed in non artisan aquifers will be sealed using cement or other <br /> suitable sealant by placing the sealant to extend 20 feet above and below the water <br /> bearing zone. A surface plug will then be placed in accordance with the above <br /> paragraph. The hole will be marked. <br /> Gob Vent Boreholes(GVBs) present unconventional circumstances for abandonment <br /> procedure to assure methane does not leak to the surface. The Mine is using a <br /> pressurized ventilation system to Apush@ methane up through the GBV's to cause <br /> exhausting of methane gas to the surface. <br /> GVB's are constructed by drilling a hole to within 30 ft. above the seam then placing a <br /> string of 5.5 or 6.5 inch casing in the hole with the open bottom of casing suspended <br /> approximately 230 feet above the seam leaving 200 ft. of open hole. The bottom 200 <br /> ft. of casing is perforated, at the top of the perforations a cement basket is placed <br /> and cement is pumped into the annulus above the basket completely grouting the <br /> casing in-place. This provides at least 200 ft. of fully grouted casing, in the worst <br /> case scenario (GVB-4-D-A), where the total depth of he hole is 500 ft. and the <br /> amount of perforated casing was adjusted to 100 ft. Typically hole depths are in <br /> excess of 1000 feet which results in the grouted interval (fully cemented to the <br /> formation) in excess of 600 ft. <br /> GVB's will be sealed as follows: <br /> 1. The condition of borehole will be verified by sounding the total depth of <br /> the borehole. <br /> 2. A bridge plug will be placed at the lowest point possible in the blank <br /> casing. The bridge plug will always be placed above the perforated <br /> casing. <br /> TR-123 2.05- 81 03/22 <br />