2011-06-20_PERMIT FILE - C1982056A (6)

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approximately 300 ft x 40 ft, or 0.28 acres) the active pipeline construction areas meet the applicable criteria for a Small Area Exemption, and construction of full -scale drainage and sediment control structures is neither needed nor justified. • 19RT Mine Dewaterinst Borehole and Pipeline (TR10 -73) During construction, and for the minor surface structures that will remain during mining, drainage and sediment control for the 19RT Mine Dewatering Borehole and Pipeline will be provided by Alternative Sediment Controls (ASC's) consisting of combined Best Management Practice (BMP) measures. BMP's for the construction activities include: • Minimizing the area of surface disturbance • Scheduling of construction activities during the dry summer period • Placement of staked straw wattles downgradient of all surface disturbance areas to intercept any surface runoff and trap associated suspended solids • Soil replacement and stabilization with either the standard rangeland or pastureland seed mixtures (as appropriate) in a timely manner following completion of construction activities Construction- related surface disturbance will be limited to soil removal and windrowing from the pipeline trench alignments and stockpiling for the borehole pad area, excavation of the trenches and temporary stockpiling of excavated material adjacent to the trench, minor cut/fill grading to establish the borehole drill -pad, and excavation of temporary cuttings pits. Where pipeline disturbance traverses steep slopes, additional staked straw wattles will be placed on- contour to limit overland flow following revegetation seeding. Drainage and sediment control for the associated minor surface structures (borehole surface casing and any manhole(s)) will also utilize BMP's including the vegetative filter provided by temporary vegetative stabilization, and berms and/or wattles, as appropriate. The pad for the 19RT Mine Dewatering Borehole installation has been designated as a Small Area Exemption (SAE), and the limited drainage from this small area (0.35 acres) will be controlled by staked straw wattles, and reclamation/stabilization of the pad area • following well installation. Temporary drainage and sediment control measures will remain in -place until vegetation is sufficiently established to effectively control runoff, erosion, and sediment loss. As relatively small isolated surface disturbances, the additional disturbance required to construct ditches and sedimentation ponds to intercept, route, and treat runoff from the dewatering borehole pad, is not warranted. Similarly, for the associated temporary linear pipeline disturbances, construction of ditches and ponds to control runoff is impractical. Runoff from these small disturbance areas will move downslope toward Fish Creek through areas of extensive natural vegetation, which will supplement the ASC's, effectively serving as a vegetative filter. The proposed BMP's have proven effective in controlling runoff and sedimentation from similar disturbances. Special design, construction, and operational measures have been incorporated in the design plans to assure that there will be no discharge or mixing of mine water with surface drainage. Following installation of appropriate ASC's for each portion of the project disturbance, available soil materials will be bladed from any new disturbance areas and temporarily windrowed or stockpiled on the upgradient edge of these disturbance areas. For pipeline trench areas, consideration of soil horizon segregation must be balanced with the objective of limiting overall surface disturbance. In the interest of minimizing overall surface disturbance, TCC proposes to not segregate and separately stockpile individual soil horizons for the pipeline trench disturbance, and submits that this approach will not significantly alter soil suitability characteristics, since the differences between the soil horizons is not significant over the areas to be affected by trenching. For the borehole drill -pad, individual soil horizons will be segregated, if present. Soil materials will be replaced following completion of pipeline installation. Reseeding of the disturbed areas will be completed during the first appropriate planting period following soil material replacement. When no longer needed to support ongoing or future mining and related operations, the thickener underflow borehole will reclaimed •by removing the surface manhole structure, plugging and sealing the borehole, consistent with State Engineer requirements; cutting -off the casing below ground level, and placing a permanent marker; then regrading, replacing soil materials, and reseeding the associated disturbance areas., Pipelines will be abandoned in- place, with the ends of the pipelines cut -off and capped below grade. MR 10 -251 2.05 -84.8 05/27/11