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

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A second 14.75 -inch diameter Utility Borehole will be completed to a depth of approximately 1,390 feet. A 60 -foot deep, 16 -inch diameter surface borehole and surface casing will first be completed to support subsequent drilling operations. The Utility Borehole will be completed with a 13 -inch diameter grouted steel casing, an 8.625 -inch and a 4.5 -inch diameter pipes will be installed within the casing, and the annulus will be grouted between the borehole and casing. It is anticipated that the 8.625 -inch pipe will be used as a rock -dust drop, and the 4.5 -inch pipe for compressed -air. The additional 18LT Rock -Dust Tank Installation will consist of a new rock -dust tank, which will be mounted on four poured concrete piers; a connection to the new borehole; required electrical and control equipment, that will tie -in to the existing 18LT Substation; and a dust collection system. The MCC Building installation includes a 40 x 40 foot concrete pad and steel building and an 8 x 48 foot exterior concrete pad. In order to accommodate the three large air compressors necessary to meet mine compressed air requirements, the exterior concrete pad will be extended to 24 x 56 feet. Fourteen, 12 -inch diameter holes will be bored approximately 20 feet to bedrock, and surface materials in the pad extension footprint will be over - excavated, replaced, and re- compacted. Reinforced concrete piers and pad will be pored to support the compressors and a pre- fabricated steel building will be constructed on the extended pad to enclose the compressor installation. Following commissioning, the shaft pad site, access road, and pipeline corridor will be cleaned -up and surface areas graded and stabilized by seeding with the temporary seed mixture. When these facilities are no longer needed to support ongoing or future mining and related operations, reclamation will involve removal of surface structures and facilities, demolition of concrete foundations and pads, disposal of concrete debris in the shafts, replacement of cuttings from the temporary cuttings pits in the shafts, grading of disturbance areas to blend with the surrounding terrain, soil material replacement, and reseeding with the appropriate permanent revegetation seed mixture (Pastureland Mixture for Shaft site and road, and Rangeland Mixture for Pipeline corridor). Boreholes will be plugged and sealed in accordance with applicable State Engineer requirements, and pipelines will be cut -off below grade, capped, and buried in- place. WMD Stabilization Boreholes (MR11 -253) In order to address immediate safety and operational concerns associated with localized ground stability issues, TC drilled two stabilization boreholes in the 17 -Left Gateroad to allow concrete to be pumped into gateroad and crosscut areas, forming a series of supplemental support pillars. Activities associated with this ground stabilization effort included; • Establishment of temporary drainage and sediment control measures • Soil material removal and placement in a temporary stockpile • Construction of a short temporary access road • Construction of a 200' x 300' drill pad • Drilling and casing of 2 boreholes from the pad • Set -up of a portable concrete batch plant on the existing 18 -Left Shaft Pad, or direct delivery of pre -mixed concrete to the borehole site • Extension of a temporary concrete transfer line on the ground surface between the batchplant and the drill - site • Pumping of concrete down the drillholes into the underground workings • Plugging and sealing of the drillholes • Reclamation and restoration of all related temporary surface disturbance The location and configuration of the proposed activities are shown on Figure 49U -F1, WMD Stabilization Boreholes. Temporary drainage control and sediment control measures for these activities include placement of a 36 -inch x 80 foot CMP culvert in the borrow ditch for County Road 27 to allow road runoff to pass under the temporary access road (culvert is sized to match the existing downgradient culvert crossing under the road), construction of a temporary diversion ditch and catch basins upgradient of the drill pad to intercept and route any natural runoff around the pad, and placement of straw wattles downgradient of the pad to intercept and control any runoff that escapes the pad. Temporary drainage and sediment control measures will be in -place before any other activities proceed. MR11 -253 2.05-45.20 04/18/11