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<br />possible under optimal conditions; however, with Trapper’s thin and steeply dipping coal seams much <br />shorter penetrations are anticipated, (1,200 feet are shown). <br /> <br />Trapper is not currently aware of any abandoned or active underground mine workings in any of the <br />pertinent coal seams in the proposed highwall mining areas. In the event abandoned or active <br />underground mining operations are identified, no highwall mining will be conducted within 500 feet of any <br />underground workings in the applicable seams. A protective buffer of 200 feet will be left in place <br />between the north wall of the old F Pit and the southernmost extent of the N Pit south highwall mining. <br /> <br />Trapper is also not aware of any dwellings, buildings, tanks, impoundments or utilities overlying areas <br />planned for highwall mining. Subsidence is not anticipated with any highwall mining activities at the site. <br />Design criteria established by Agapito Associates Inc. (Summary of Geotechnical Design and Operational <br />Considerations for Highwall Mining-I, J, N and L Pits, Trapper Mine; January 2, 2020; Page(s) 3-1, 6-3), <br />will be utilized to ensure long-term stability of highwalls and mining areas based on seam and overburden <br />thickness. <br /> <br />Access to highwall miner entries will be blocked or buried within 30 days following coal extraction. <br /> <br />Any highwall mining entry discharging water containing toxic-forming or acid-forming material will be <br />plugged within 72 hours after completion by backfilling and compacting non-combustible and impervious <br />material into the hole to a depth sufficient to form a water-tight seal or the discharge will be treated within <br />72 hours after completion to meet applicable effluent limitations and water quality standards. <br /> <br />3.1.5 Reclamation Plan <br /> <br />Following mining, pits are backfilled as a part of the overburden and interburden removal operation. The <br />backfilling operations are accomplished in different ways, depending on the equipment utilized in <br />overburden removal operations. <br /> <br />In a typical dragline operation, as the dragline excavates a pit, the overburden/interburden material is <br />spoiled (backfilled) into the previous pit (see fig. 3.5-2 A). The backfill material is placed in piles that require <br />additional contouring. Contouring is accomplished with dozers, graders and similar equipment. <br />Occasionally, the dragline is also used. <br /> <br />In Multiple Equipment operations, the dragline may be assisted by truck/loader (or excavator) operations <br />and dozer stripping operations. Dozers are utilized to remove interburden material from the “K”, and “L” <br />coal seams. The Dragline operation removes the “M” and “Q” interburdens, and the Truck/Loader fleet <br />removes the surface overburden and the “H”, and “I” interburden material. The Truck/Loader Operations, <br />as well as the dozer operations, are generally operating several cuts ahead of the dragline operation. <br /> <br />In the Multiple Equipment scenario, the dozer fleet pushes the interburden material perpendicular to the cut <br />and into the prior pit. This interburden becomes the first material backfilled into the previous pit and therefore <br />is at the bottom of the backfill sequence. The dragline excavates the lower interburden material above the <br />“M” and “Q” seams and places it on top of the material placed in the prior cut by the dozer fleet. This dragline <br />spoil is the intermediate layer of material within the backfill sequence. The final layer in the backfill sequence <br />is placed by the truck/loader operations. This material is placed in dumps that are in close proximity to the <br />post mining topography (PMT). The final contouring is accomplished with dozers, graders and similar <br />equipment (see Fig. 3.5-2 B). <br /> <br />In the case of Ithaca and Jennings Pits, the backfill will occur as one pit is developed, a previously mined <br />pit is backfilled. The initial pit overburden will be stockpiled south of the BC haulroad, just east of No Name <br />pond #2. Approximately 600,000 LCY’s of material will be placed in a temporary spoil pile here, and will <br />remain until the final pit is ready to backfill. The final contouring is accomplished with dozers, graders and <br />similar equipment. <br /> 3-15c