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As part of the 18 -Left Shaft project, TCC will complete a 14.75 -inch diameter borehole to a depth of approximately <br />1,360 feet. The borehole will be completed with a 13 -inch diameter steel casing, a 6.625 -inch and two, 5.0 -inch <br />diameter pipes will be installed within the casing, and the annulus will be grouted between the borehole and casing. <br />It is anticipated that the 6.625 -inch pipe will be used as a mine dewatering borehole, and the two 5.0 -inch pipes for <br />power drops or communication lines. <br />Water from the WMD will be collected in a series of sumps, transferred to a pump station at the bottom of the 18- <br />Left Shaft, and pumped to the surface by a 320 HP high- capacity submersible pump, at a maximum rate of <br />approximately 700 gpm. A new pipeline running approximately 8,200 feet from the 18 -Left Shaft site to the <br />southeast, will connect to the existing Fish Creek Mine Water Transfer Pipeline just to the east of the Fish Creek <br />Water Treatment Facility. The 18LT Pipeline will be a 12 -inch HDPE pipeline with thermally- welded joints, <br />buried below the frostline at a depth of approximately 5 feet. The pipeline will be installed under Routt County <br />Road 27 by boring or jacking the pipeline under the road, and a crossing of Fish Creek will be either trenched <br />through the creek during the winter low -flow period, or bored under the creek. Permitting for pipeline installation <br />includes approvals from the U.S Army Corps of Engineers (Nationwide Permit 12), CDPHE — Water Quality <br />Control Division (Construction Dewatering Permit), notification of the Colorado Division of Water Resources, and <br />a County Utility Install Right -of -Way Permit, as appropriate. <br />Pipeline construction will involve placement of sediment control materials (straw wattles or silt fence) downslope <br />of the disturbance at any location where the pipeline corridor is within 50 feet of a Stream Buffer Zone or non- <br />qualifying ephemeral drainage; removal and windrowing of available soil material (total soil material volume for <br />the pipeline project is estimated at 12,150 cy) to one side of the 40 foot pipeline construction corridor; excavation <br />of the pipeline trench using a track -hoe, with temporary placement of the excavated material on the opposite side of <br />the trench; placement, connection, and bedding of the pipe; backfilling and compaction of the excavated material <br />around the pipe; re- spreading of the soil material; and re- seeding using the standard rangeland seed mixture. Where <br />the pipeline is installed by boring, boring pits will be excavated within the pipeline construction corridor for the <br />boring equipment and pipe handling. Because the soil materials will be replaced immediately after pipeline <br />placement, as construction advances, stabilization measures are not necessary. <br />Where the pipeline crosses under Routt County Road 27, boring or jacking pits will be excavated on the edges of <br />the road right -of -way, and the pipeline will be bored or jacked under the road. The Fish Creek crossing has been <br />located to take advantage of a deeply incised stream channel, minimizing potential impacts to the narrow riparian <br />fringe which exists along this section of the creek. Because pipeline installation activities will occur within Stream <br />Buffer Zones, TCC is requesting a variance from the Stream Buffer Zone requirements, consistent with the <br />applicable provisions of Rule 4.05.18. To the extent feasible, the trenched crossing will be completed during the <br />winter low -flow period. A temporary upstream flow barrier will be established in the channel, and normal <br />streamflows will be transferred around the work area by pumping from the resulting pool above this upstream <br />barrier to well below the crossing work area. Pumping capacity will be approximately 10 cfs (greater than <br />maximum measured historic flows for the construction timeframe) to assure that there is no diminution of flow, and <br />back -up pumping capacity will be provided in the crossing construction area to address any leakage or underflow. <br />Details of the Fish Creek pipeline crossing are presented in Exhibit 49R, 18LT Ventilation Shaft Installation — <br />Design Drawings. If the Fish Creek pipeline crossing is completed by boring the pipeline under the creek, the <br />surface protective measures, as outlined above, will not be necessary. <br />Protective measures (BMP's) at the crossing location will include placement of stream buffer zone markers at any <br />point where the pipeline corridor is within 50 feet of the stream buffer zone prior to any activity; placement of silt <br />fence or anchored straw bales at least 50 feet downstream to catch any sediment released prior to initiation of work; <br />placement of sediment control materials (straw wattles or silt fence) around the entire side and near stream <br />perimeters of the pipeline excavation and stockpile disturbance areas on both sides of the stream; restrictions on <br />storage or transfers of petroleum products within the buffer zone, and reclamation of the affected areas immediately <br />following completion of pipeline installation. These measures should be effective in assuring compliance with <br />applicable provisions of Rule 4.05.18 (1)(a) through (c). Construction and sediment control details are shown by <br />the design drawings in Exhibit 49R. Manholes, consisting of 8 -foot diameter x 10 -foot high CMP culverts, fitted <br />with locking lids and access ladders, will be installed at either end of the pipeline for access to pipeline valving. <br />MR10 -250 2.05-45.19 12/02/10 <br />