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Mountain Coal Company Exhibit 69 <br /> West Elk Mine Sylvester Gulch Facilities <br /> • safety factor of 1.2 per Rule 4.05.9(8)(a) for high-hazard facilities). The impoundment does not <br /> fall within the Class B or Class C criteria for dams (USDA,,SCS Technical Release No. 60), and <br /> thus does not require compliance with the "Minimum Emergency Spillway Criteria'' (Rule <br /> 4.05.9(2)(d)) or the safety factors required by Rule 4.05.9(8)(a), although it meets these criteria. <br /> Embankments will be constructed in accordance with Rule 4.05.9(7). The embankment crests <br /> will have 6 inches of gravel placed for access and the external embankment side slopes will be <br /> covered with approximately 12 inches of topsoil. The topsoiled areas will be seeded and <br /> mulched with tackifier or erosion control mats in conformance with Rule 4.05.9(9). Larger rocks <br /> from the excavation will be placed along the embankment toes for added stability and erosion <br /> control. Two settlement mor:uments will be placed on the crest, one at the northeast corner and <br /> one at the southeast corner of the pond embankment. One piezometer will be installed through <br /> the northeast pond embankment and into the subsurface soils. <br /> The Second Pond will be prepared to design lines and grades prior to installation of either a 60- <br /> mil high density poly thylene (HDPE) or a 45-mil reinforced polypropylene geomembrane liner. <br /> A minimum 4-inch thick sand layer or a thick non-woven geotextile will be placed underneath <br /> the geomembrane liner to protect the liner from underlying rocks in the excavation. <br /> The estimated capacity of the Second Pond will be approximately 1.2 million gallons. This will <br /> provide a residence time in excess of 48 hours for the design flow rate of 400 gpm, assuming a <br /> maximum of 2 feet of sediment in the pond. As with Pond 017, the Second Pond will only <br /> • receive and manage mine water. <br /> The normal freeboard in the Second Pond will be 2 feet between the normal operating water <br /> surface El. 6818 ft MSL and the pond crest El. 6820 MSL. The minimum freeboard in the <br /> Second Pond will be at least 1.3 feet below the settled embankment (El. 6819.8 min),with peak <br /> flows through the pond occurring at water surface El. 6818.5. This is in excess of that required <br /> by Rule 4.05.9(7)(d). <br /> A 6-foot high chain link security fence will be placed around the Second Pond and will tie into <br /> the existing fence at the north and south ends of the existing Pond 017. <br /> Overall Treatment Process <br /> A preliminary process flow diagram plan and profile is shown on the attached Sheet PF-I. Based <br /> on previous data for iron concentrations in discharge from Pond 017, it anticipated that the lower <br /> discharge rate and increased residence time and aeration provided with the revised system will <br /> provide for compliance with discharge standards. Therefore, under typical conditions, the ponds <br /> may operate as a relatively continuous flow-through system. However, the system is designed to <br /> accommodate a batch flow system if additional aeration and/or residence time are needed to <br /> reduce Fe and TSS levels for discharge compliance. <br /> • <br /> 5 <br /> Rev.10/97-TR83,Rev.04/09-TR116 <br />