2011-06-20_PERMIT FILE - C1982056A (8)

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stormwater diversion channel are designed to safely pass the peak discharge (approximately 125.5 cfs), and the total runoff, respectively from the design storm event. On the edge of the Reservoir, near the embankment, a pump platform will be constructed, with a suspended 50 HP high- capacity submersible pump, pumping mine water from the Reservoir at a rate of up to 1,000 gpm to the Million - Gallon Tank at 6MN (MR06 -210), which is set -up to gravity -feed to the mine water system through the existing mine water utility borehole. A pad and short (130 feet) light -use road segment will provide access for inspection and maintenance. The approximately 1,400 foot pipeline from the 6MN Reservoir to the Million - Gallon Tank and utility borehole will also be 10 -inch HDPE pipe buried to a depth of approximately six feet within the previously disturbed 6MN road right -of -way. Pipeline construction disturbance will be reclaimed concurrently with pipeline installation, with backfilling, soil replacement, and reseeding using the standard rangeland seed mixture. In order to assure adequate and consistent water quality for the feed to the mine water system, the 6MN Mine Water Storage Reservoir installation will include some basic water treatment measures, potentially including one or more aerators, floating baffles within the pond, and a simple filtration system in the discharge pipeline between the Reservoir and the Million - Gallon Tank. If it is determined that additional treatment measures are necessary, any significant modifications will be addressed by a future revision. TCC will remotely monitor and control reservoir water level, and mine water discharge to and from the 6MN Storage Reservoir, to maintain the water level at or below design storage capacities, and to maintain the design freeboard, at all times. Water level and pump control interfaces will provide for integrated control of pumping systems to balance inflow and discharge and shut -off the deep well pump if the pond level reaches a certain pre -set threshold level(s), and an integrated alarm system will remotely notify the operator of any system failure, malfunction, or water level concern. These controls will also assure that adequate storm -water storage capacity is maintained at all times. Electrical power for the 6MN Reservoir discharge pump, aerators, and control systems will be provided by a short (approximately 300 feet) distribution line from the existing substation at the 6MN Shaft pad. Construction of this short line segment will require the installation of 3 powerpoles. Also, a short light -use road, approximately 300 feet in length, will be constructed to the pond pump- station from the existing 6MN Shaft pad access road. The location, configuration, and components of the 6MN Mine Water Storage Reservoir installation are shown on Map 24 (sheet 2 of 3), Surface Facilities and Freshwater Systems. Related design information is provided in Exhibit 490, 6MN Mine Water Storage Reservoir — Design Drawings, including a design stability analysis for the pond embankment. Because the proposed Reservoir storage volume is greater then 20 acre -feet, design and compliance documentation have also been submitted to the Mine Safety and Health Administration (MSHA) for review and approval. 18 -Left Mine Ventilation Shaft Installation (MR09 -235) As the basis for design and construction of two proposed mine ventilation shafts and associated ancillary facilities, TCC will conduct geotechnical investigations for the 18 -Left (18LT) Mine Ventilation Shaft Installation. The site will be accessed using a Snow -Cat mounted auger, and the geotechnical investigations will involve completion of up to eight 4 -6 inch hollow -stem auger sample holes and collection, examination, and testing of the resulting samples. Auger test holes will be located by the contractor within the areas defined as the 18LT shaft pad and road areas, as shown on Figure EX49R -F1, and will be advanced to depths of 15 -40 feet. On completion of each sample hole, the hole will be backfilled with drill cuttings and leveled. Given that all sample holes will fall within the 18LT shaft facilities footprint, and shaft facility construction is anticipated within the next six months, further reclamation will not occur unless shaft facility construction is deferred or cancelled. In those circumstances, drill - sites will be seeded with the approved rangeland seed mixture during the first scheduled seeding operations follow the decision to defer of cancel shaft construction, but no later than nine months following completion of sampling activities. MR10 -250 2.05 -45.14 12/02/10