2025-01-07_PERMIT FILE - C1996083 (5)

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2.05.4(2)(e) (2)(g) Sealing or Managing Mine Openings, Exploration Holes, Other Boreholes or Wells The mine portals will be sealed in accordance with Map 28, Portal Entry Seals and Map 30 Portal Entry Water Tight Seals. Vent shafts will be sealed in accordance with Map 29 Shaft Seals. The exploration and monitoring holes will be sealed in accordance with the requirements of Rule 4.07. Two types of seals were considered for installation at the Bowie #2 Mine. If mine water in-flows are experienced in the mine, a water-tight seal as shown on Map 30 may need to be installed to plug the portals and contain potentially degrading mine water from flowing from the abandoned portals. It is highly unlikely mine water will build up behind the portal seals since the dip of the mine workings is 2 to 5 degrees to the northeast. Additionally, the mine has been idle since February 29, 2016, and there is no indication water has reached the portals. The Operator intends to seal the portals as shown on Map 28. The dip of the mine workings will prevent acid or other toxic drainage for entering surface waters and will minimize disturbance to the prevailing hydrologic balance. Although water-tight seals are not required, the design will be maintained in the permit. The design of the concrete water-tight seal was taken from Bureau of Mines Information authored by Cheken, Garrett, and Pitt. They developed an equation used for design after work done in Africa on seals which where able to withstand hydrostatic pressure in excess of 6,000 psi. The equation is as follows; L = (p*a*b)/((a+b)*fc) where; L = Length of plug, ft. a = width of entry, ft. b = Height of entry, ft. p = Hydrostatic pressure, psi. fc= Allowable compressive strength of rock or concrete, whichever is the lesser, psi. The height and width, a and b, of the portal entries is 8-feet and 20-feet, respectfully. The roof, ribs and floorwill be cleaned to competent material but will not be recessed into solid rock or coal. The maximum calculated hydrostatic pressure, p, for the seal will be 60-feet of water or 26 psi (measured from the seal elevation to the piezometric surface of the upper perched water bearing zone). Coal will have the lowest compressive strength, and triaxial tests preformed on the coal typically average 1000 psi. Garrett Campbell and Pitt recommend the use of a factor of safety of 4 to 5. The allowable compressive strength will be (1/5)*(1000)= 200 psi. Using this data, the length of the plug required would be 0.75'. The applicant would like additional TR-101 2.05- 80 03/22