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Reservoir and the Million -Gallon Tank. If it is determined that additional treatment measures are necessary, any
<br />significant modifications will be addressed by a future revision.
<br />TCC will remotely monitor and control reservoir water level, and mine water discharge to and from the 6MN
<br />Storage Reservoir, to maintain the water level at or below design storage capacities, and to maintain the design
<br />freeboard, at all times. Water level and pump control interfaces will provide for integrated control of pumping
<br />systems to balance inflow and discharge and shut-off the deep well pump if the pond level reaches a certain pre-set
<br />threshold level(s), and an integrated alarm system will remotely notify the operator of any system failure,
<br />malfunction, or water level concern. These controls will also assure that adequate storm -water storage capacity is
<br />maintained at all times. Electrical power for the 6MN Reservoir discharge pump, aerators, and control systems will
<br />be provided by a short (approximately 300 feet) distribution line from the existing substation at the 6MN Shaft pad.
<br />Construction of this short line segment will require the installation of 3 powerpoles. Also, a short light -use road,
<br />approximately 300 feet in length, will be constructed to the pond pump -station from the existing 6MN Shaft pad
<br />access road.
<br />The location, configuration, and components of the 6MN Mine Water Storage Reservoir installation are shown on
<br />Map 24 (sheet 2 of 3), Surface Facilities and Freshwater Systems. Related design information is provided in
<br />Exhibit 490, 6MN Mine Water Storage Reservoir — Design Drawings, including a design stability analysis for the
<br />pond embankment. Because the proposed Reservoir storage volume is greater than 20 acre-feet, design and
<br />compliance documentation have also been submitted to the Mine Safety and Health Administration (MSHA) for
<br />review and approval.
<br />Following construction and filling of the 6MN Mine Water Storage Reservoir, it was noted during regularly
<br />scheduled inspections that precipitation and runoff was collecting and pooling in a low area just off the south toe of
<br />the Reservoir embankment. This was a concern due to the potential to mask any indication of seepage from the
<br />Reservoir and the potential to affect the stability of the Reservoir embankment. In order to address this concern,
<br />two connecting drainages (total length is a maximum of 400 feet) were established to drain any standing water
<br />away from the toe, toward a minor ephemeral tributary to Fish Creek. Drainage construction involved removal of
<br />soil and vegetation, drainage excavation, placement of flow controls in the drainage channels to limit flow velocity
<br />and erosion, soil replacement, and reseeding. As minor surface features which have been revegetated and which
<br />will eventually silt in, the drainage segments will be retained, and will not be reclaimed.
<br />18 -Left Mine Ventilation Shaft Installation (MR09-235)
<br />As the basis for design and construction of two proposed mine ventilation shafts and associated ancillary facilities,
<br />TCC will conduct geotechnical investigations for the 18 -Left (18LT) Mine Ventilation Shaft Installation. The site
<br />will be accessed using a Snow -Cat mounted auger, and the geotechnical investigations will involve completion of
<br />up to eight 4-6 inch hollow -stem auger sample holes and collection, examination, and testing of the resulting
<br />samples. Auger test holes will be located by the contractor within the areas defined as the 18LT shaft pad and road
<br />areas, as shown on Figure EX49R-F1, and will be advanced to depths of 15-40 feet. On completion of each sample
<br />hole, the hole will be backfilled with drill cuttings and leveled. Given that all sample holes will fall within the
<br />18LT shaft facilities footprint, and shaft facility construction is anticipated within the next six months, further
<br />reclamation will not occur unless shaft facility construction is deferred or cancelled. In those circumstances, drill-
<br />sites will be seeded with the approved rangeland seed mixture during the first scheduled seeding operations follow
<br />the decision to defer of cancel shaft construction, but no later than nine months following completion of sampling
<br />activities.
<br />18 -Left Ventilation Shaft (MR09-235, MR10-249, MR10-250, TR 09-66, TR09-70)
<br />As mine development proceeds to the west in the Western Mining District (WMD), the distance from existing mine
<br />ventilation shaft and fan installations will increase to the point where additional intake and exhaust ventilation
<br />shafts are necessary to maintain effective ventilation of active mining areas. In order to minimize surface
<br />disturbance and simplify operation, the new intake and exhaust shafts will be established at the same location. The
<br />proposed new ventilation shafts will be located in close proximity to Routt County Road 27 in the NW'/SW'/
<br />Section 23, TSN, R87W on a shallow slope near the crest of a small ridge in an area of open pastureland, as shown
<br />on Map 23. Development, construction, and installation of the ventilation shafts and associated fan and ancillary
<br />MRI 1-259 2.05-45.15 11/17/11
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