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I ? t Peabod Twentymile Coal 29515 Routt County Road 27 Oak Creek, CO 80467 970.879.3800 Mr. Paul Perri, P.E. February 1, 2010 Division of Water Resources Office of the State Engineer - Dam Safety Division 1313 Sherman Street -Room 818 Denver, Colorado 80203 303.866.3581 Re: Twentymile Coal Company - 18-Left Mine Water Pipeline Crossing of Fish Creek, Temporary Construction Measures Dear Mr. Perri: Twentymile Coal Company (TCC) proposes to construct a water pipeline crossing of Fish Creek. TCC has submitted required permit applications for this project to the Colorado Division of Reclamation, Mining, and Safety, Colorado Department of Public Health and Environment - Water Quality Control Division, and the U.S. Army Corps of Engineers (under Nationwide Permit 12). The proposed water pipeline will extend from our new 18-Left Shaft location to the southeast, a distance of approximately 8,200 feet, connecting to the existing Fish Creek Mine Water Transfer Pipeline just to the east of the Fish Creek Water Treatment Facility, as shown by the accompanying Figure 1. The pipeline will be a 12-inch HDPE pipeline with thermally-welded joints, buried below the frostline at a depth of approximately 5 feet. Pipeline routing has been carefully delineated to minimize potential environmental impacts, and facilitate construction. The pipeline will cross under Routt County Road 27 (requires a Utility Install Right-of-Way Permit from Road & Bridge Department) and will require a crossing of Fish Creek, a perennial stream. Fish Creek is a small perennial stream flowing through Twentymile Park. The flow regime for Fish Creek is characterized by high spring flows during and following snowmelt (April through late-June), with significantly reduced flows (2-1 Ocfs) throughout the remainder of the year, and low flows during winter (2- 6cfs, November through March). With low stream gradients through much of the Twentymile Park Basin, the channel configuration for Fish Creek includes an incised (deeply in some areas) channel, numerous narrow meanders, and a poorly developed floodplain. The pipeline crossing location for Fish Creek has been specifically selected to take advantage of a deeply incised segment of the channel where disturbance will be minimal. TCC also proposes to complete the channel crossing work during the low-flow winter period (February through March) when streamsflows are at a minimum, and there is little potential for significant runoff. Construction of the pipeline crossing will involve the following sequential activities, as illustrated by the accompanying Figure 3 (Figure 2 shows the County Road crossing): Install staked (rebar) straw bales and silt fence approximately 50' downstream of the downstream edge of the crossing disturbance area to intercept any sediment generated during construction Locate a portable pump, with suction-line in the stream, approximately 50' upstream of the upstream edge of the crossing disturbance area. The pump will be sized to handle the maximum recorded historical flows (1 Ocfs) during the construction period. The pump discharge will be located at least 20' upstream from the previously placed straw bales and silt fence, and will be installed to prevent channel scour (may involve placement of a rock discharge apron, depending on conditions) Install a staked straw bale flow barrier (staked straw bales at least three bales thick, and as high as necessary to limit flows), with a low-permeability upstream facing material (reinforced tarps or brattice