2010-06-04_PERMIT FILE - C1982056A (9)

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pilings. Preparation of the tank foundation area will involve grading, compaction, and excavation for the support pilings and spread- footer. Following site preparation, the reinforced concrete pilings and footers will be formed, and poured, followed by the reinforced concrete pad and stem wall. The , steel tank will be fabricated in sections which will be placed and anchored on the stem wall. A water -tight liner system will complete the tank installation. A buried 8 -inch HDPE line will connect the tank to the water borehole for both filling from and discharge to the mine water system. Pumps (both underground and at the surface) and control sensors and valving will allow for controlled flow in either direction in the supply system. Tank fill sensors and a monitored overflow drain will be installed in the tank to prevent overfilling. The overflow drain line will be installed in the same trench as the water supply and return line and will drain back to the mine -water handling system. A small 8 x 8 foot pumphouse, will be constructed next to the tank on a concrete foundation to house pumps and valves. Power and/or control communications will be laid in conduit above the waterline connecting the tank and the borehole. The locations for the seven boreholes for project utility components are shown on Maps EX16E -M1 and M2. As shown on Map 23, additional entries will be driven to the south of the 6 North Main entries to connect with the ventilation shaft. These entries will be needed to maximize the efficiency of the ventilation system. The entries will be driven in the same manner as is used in TCC's development work, i.e. continuous miners and shuttle cars. Following commissioning of the shaft, the shaft pad site and access road will be cleaned -up and surface areas graded and dressed. In addition to the direct piped connection to the mine -water system at 6MN, the Million- Gallon Tank will be temporarily connected directly to a pipeline running from the 10 -Right Mine Dewatering Pipeline. Water from the 10 -Right Mine Dewatering Well, which pumps accumulated mine inflows from a sump in the sealed Eastern Mining District, is pumped to the surface by a 320 HP high- capacity submersible pump, at a rate of approximately 700 gpm. The pump discharge is currently transferred by a series of surface and underground pipelines to the Area 1 Pit in the TCC Mine Facilities Area for use in either coal preparation operations or for storage and subsequent use as a back -up source for the operational mine water system. • As part of the 6MN Facilities project, TCC will establish a new pipeline running approximately 7,750 feet from the 10 -Right Dewatering pipeline to the 6MN Storage Reservoir. The pipeline will be constructed of 10 -inch HDPE pipe, buried to a depth of approximately six feet, with one sub -grade crossing (bored under) of Fish Creek. Details on the Fish Creek pipeline crossing are presented in Exhibit 490, 6MN Mine Water Storage Reservoir — Design Drawings. Pipeline construction will involve placement of sediment control materials (straw wattles or silt fence) downslope of the disturbance at any location where the pipeline corridor is within 50 feet of a drainage or stream buffer zone; removal and windrowing of available soil material (total soil material volume for the pipeline project is estimated at 11,150 cy) to one side of the 50 foot pipeline construction corridor; excavation of the pipeline trench using a track -hoe, with temporary placement of the excavated material on the opposite side of the trench; placement, connection, and bedding of the pipe; backfilling and compaction of the excavated material around the pipe; re- spreading of the soil material; and re- seeding using the standard rangeland seed mixture. Because the soil materials will be replaced immediately after pipeline placement, as construction advances, stabilization measures are not necessary. Where the pipeline crosses under Fish Creek, jacking pits will be excavated adjacent to the creek, while maintaining a minimum 5 -foot buffer between the near edge of the pits and the crest of the stream bank, and the pipeline will be bored or jacked under the creek. Protective measures (BMP's) at the crossing location will include placement of stream buffer zone markers at any point where the pipeline corridor is within 50 feet of the stream buffer zone prior to any activity; completion of the work during low -flows; placement of silt fence or anchored straw bales at least 50 feet downstream to catch any sediment released prior to initiation of work; placement of sediment control materials (straw wattles or silt fence) around the entire side and near stream perimeters of the jacking pit disturbance areas; restrictions on storage or transfers of petroleum products within the buffer zone, and reclamation of the affected areas immediately following completion of pipeline installation. Construction and • sediment control details are shown by the design drawings in Exhibit 490. With construction of the 6MN Mine Water Storage Reservoir, the temporarily direct connection from the 10 -Right Mine Dewatering Pipeline to the 6MN Million - Gallon Tank will be replaced with an inlet line from the 10 -Right TR06 -57 2.05 — 45.6f 07/28/09