2017-07-12_PERMIT FILE - C1981012 (3)

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where: S 1 2 = release area variance S 2 2 = reference area variance if i = release area sample size, and nz = reference area sample size. The results of sampling efforts will be contained in the annual reclamation report. Ilse presentation will include the raw field data, a summary of the analyses, and the results of the analyses. On August 15, 1985 (revised December 8, 1986) Basin submitted if rill and gully plan to the Division. Exhibit 26, Rill and Gully Plan, presents a copy of this plan. f). Sealing and managing Mine Openings Sealing of the openings which access the underground coal mining operations at the Golden Eagle Mine will be completed upon the final closure of the mining operations to minimize safety hazards to man and wildlife in these areas. A typical mine opening seal is shown on Figure 4. Figure 5, Typical Borehole Seal, shows a typical closure that will be utilized by Basin, except as described in Section 2.05.4 g). The airshaft known as the Northwest Bleeder Shall, originally schedule to he developed for methane gas production, never received permit approval bonding through the Colorado Oil and Gas Conservation Commission. Alternatively, the following abandonment pan will be innplennentcd: g). Northwest Airshafl Abandonment Plan The Northwest Airshaft, a 605 foot shaft completed to an eight foot diameter, was constructed by raise - boring a ten foot diameter opening. This opening was lined to an eight foot diameter with perforated steel plate. The annulus was cemented at the bottom to a height of 15 feet, tilled with pea-sized gravel to fifteen feet from the surface, and capped with 15 feet of cement. At mine closure a cement cap was constructed over the surface opening. The mine has flooded since closure and the water level is currently approximately thirty feet above shaft bottom. The airshaft will be backfilled and grouted as detailed by Figure 7 - Northwest Airshatt Closure. The cement cap will be removed from the shaft opening. Approximately 25 cubic yards of 36x0 rock will be deposited at the bottom of the shaft to breach the mine opening. This will be followed by placement of pit - run material to within 25 feet of the lowest water bearing zone. Approximately 700 sacks of Baroid HolePlug followed with 25 bbls of fresh water will be placed on top of the pit run material and allowed to set-up over night to provide a seal. The depth will be checked with a %vireline to document successful placement of the seal. High yield concrete will be placed to approximately 10 feet above the highest water bearing zone. The high yield mix is formulated to flow through the liner perforations, grouting the pea gravel filled annulus of the casing and sealing the water bearing zones. The depth to top of grout will be checked to document successful grout placement. This will be followed by placement of pit run material to within four feet of the surface. The cement surface foundation of the shaft collar will be removed to a depth of' Iron- feet. Concrete debris From the cement cap and collar will be mixed with the pit -run material as the shaft is filled The remaining opening will be filled with subsoil and finished with one foot of topsoil. The area of disturbance will then be mulched with straw and bloadcasl seeded with rangeland seed mix at the rate of 25 pounds/acre. TR -55 Page 2.05-27 (Revised 12/10/03)