6 Main North Ventilation Shaft and Mine Water Storage Reservoir (TR05 48, TR07 61, TR07 62, MR06 208,
<br />MR06 210, MR06 212, MR07 224, MR08-227, MR09-234, MR15-290)
<br />When the 6 Main North Ventilation Shaft and supporting equipment and boreholes are no longer required to support
<br />ongoing or future mining operations the associated surface facilities will be removed the shaft will be plugged and
<br />sealed, and surface disturbance areas will be reclaimed. The supporting equipment and any structural steel, tanks, or
<br />building framing and siding will be removed and reused, salvaged, or disposed of off-site. Buried utilities will be
<br />stubbed -off below grade and abandoned. Concrete pads will be broken up, and foundations and piers will be demolished
<br />to at least 2 feet below grade, and the resulting concrete debris will be disposed of in the shaft opening. The shaft collar
<br />concrete will also be broken up and disposed of into the shaft opening, leaving an open space for the concrete slab and
<br />backfill material/shaft cuttings to be placed in the shaft void. A cement plug will be placed in the bottom 15 feet of the
<br />shaft and the remainder of the shaft will be filled with inert material including the shaft cuttings and collar excavation
<br />materials. A cement plug will be poured from ten feet below grade to within approximately 3 feet of the surface. The
<br />remaining 3 feet will be filled with soil and graded to blend with the surrounding terrain.
<br />As noted in the discussion of construction for the 6 -Main North Ventilation Shaft, any required pressure—grout
<br />boreholes will be sealed at the time of construction. Cement grout will be pumped through the boreholes to seal an}'
<br />wet zones encountered and the boreholes will be filled with grout and allowed to set-up on completion of grouting
<br />operations. Any surface casing extending above ground surface would be cut-off flush with or below natural ground
<br />level. At such time as the 6MN Shaft Heaters are no longer needed to address winter ventilation issues, the shaft
<br />heaters will be disconnected from the propane tank and electrical connections, the vent tubing will be disconnected,
<br />and all system components (ie: heater units, vent tubing, and propane tank) will be removed from the site. Utility
<br />boreholes will be plugged, filled to within 10 feet of the ground surface with inert material, and a cement plug will
<br />be poured from the top of the fill to within approximately 3 feet of the surface. Any surface casing will be cut-off
<br />below grade, and the remaining hole will be filled with soil material and graded to blend with the surrounding
<br />terrain.
<br />The site aeotechnical auger -holes and test pits were backfilled and leveled, and piezometers were either removed. or
<br />plugged, cut-off below the ground surface, and capped with a clay or cement cap immediately following completion of
<br />field investigations. The associated disturbed areas were seeded with the pastureland seed mixture within 6 -months of
<br />completion of the geotechnical investigations. Following removal of structures and equipment, and plugging and sealin:,)
<br />of the shaft and boreholes, any cuttings remaining in the temporary mine waste disposal pit will be covered with
<br />excavated shaft collar material. road Culverts will be removed and disposed of off-site; road -base and surfacing materials
<br />will be removed and placed on the shaft pad; and the shaft pad and access road disturbance areas will be regraded to
<br />reestablish effective drainage and blend with the surrounding terrain. Cover over any cuttings remaining in the cuttings
<br />pit will be a Illinlmllm of 2 feet of suitable material, and the postmining configuration will approximate the pre -mining
<br />contours. As -built certification will be provided to the CDMG following final closure, backfilling, and grading of the
<br />cuttings pit. Any excess road -base and surfacing materials not required to reestablish approximate original contour will
<br />be hauled off-site and disposed of Stockpiled and windrowed topsoil will then be replaced on those disturbed areas
<br />Where it was previously removed and seeded with a pastureland seed mixture.
<br />The surface disturbance resulting from construction of the mine water pipeline running from the 6MN Million -Gallon
<br />Tank to the 10 -Right Dewatering Pipeline, was reclaimed concurrently with pipeline installation. After placement of the
<br />pipeline in the excavated trench, the excavated material was backfilled into the trench and compacted around and over
<br />the pipeline, topsoil which had been windrowed to the side of the trench excavation was re -spread over the disturbed
<br />area, and disturbed areas were reseeded with the standard rangeland seed mixture. When use of the pipeline is no longer
<br />necessary to support ongoing or future mining operations, the pipeline will be plugged and stubbed -off below grade at
<br />both ends, and abandoned in-place.
<br />18 -Left Ventilation Shaft Installation (MR10-249, TR09-66, TR09-70)
<br />When the 18 -Left Ventilation Shaft, emergency hoist equipment, shaft heater, and MAC borehole(s), Utility Borehole,
<br />and rock -dust tank are no longer required to support ongoing or future mining operations, the associated surface facilities
<br />will be removed, the shaft and borehole will be plugged and sealed, and surface disturbance areas will be reclaimed. The
<br />nitrogen injection system equipment is all skid mounted, and will be removed for use at another location. The mine
<br />M R 15-294 2.05-106 02/02/16
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