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• where: s~Z =release area variance s22 =reference area variance n, =release area sample size, and n2 =reference area sample size. The results of sampling efforts will be contained in the annual reclamation repotY. 'fhe presentation will include the raw field data, a swnmary of [he analyses, and the results of the analyses. On August 1S, 1985 (revised December 8, 19ft6) Basin submitted a rill and gully plan to the Division. Exhibit 2G, Rill and Gully Plan, presents a copy of this plan. n. 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 [he final closure of the mining operations to minimize safety hazards to man and wildlife in these areas. Atypical mine opening seal is shown on Figure 4. Figure S, 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 Shag originally schedule to be developed for methane gas production, never received permit approval and bonding tlvough the Colorado Oil and Gas Conservation Commission. Alternatively, the following abandonment pan will be implemented: g). Northwest Airshaft Abandonment Plan The Northwest AirshaR, 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 [o a height of 15 fee[, filled with pea-sized gravel to fifteen feet from the surface, and capped with IS feet of cement At mine closure a cement cap was constructed over the surface opening, the area restored to approximate original contour, stockpiled topsoil spread over the surface and the area mulched and seeded in accordance with the then approved reclamation plan. The mine has flooded since closure and the water level is currently approximately thirty feet above shag bottom. Prior to beginning final abandonment, topsoil will be removed from [he area of proposed disturbance and temporarily stockpiled. The work area around the shaft will be leveled with a berm created along the out slope of the area to contain and prevent shag closure materials from leaving the closure site. Surplus materials will be pushed into the shag prior to placement of the final cement cap. The original surface water diversion ditch remains in place and will prevent sw~face water from entering the disturbance area; the berm along the outslope will prevent sediment from leaving the work site. Silt-fence and/or straw bales will be used to provide sediment control along the temporary access way and elsewhere as needed. Figure 7 details the planned work area and temporary access to be provided to the site. The airshaft will be backfilled and grouted as detailed by Figure S Northwest AirshaR Closure. The cement cap will be removed from the shag opening. Approximately 25 cubic yards of 36x0 rock will be deposited at the bottom of the shag to breach the mine opening. This will be followed by placement of pih run material to within 2S feet of [he lowest water bearing zone. Approximately 700 sacks of Baroid HolePlug followed with 25 bbls of Gesh water will be placed on [op of the pit run material and allowed to set-up over night to provide a seal. The depth will be checked with a wireline to document successful placement of the seal. TR-SS Page 2.05-27 (Revised 2/10/04)