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As relatively small isolated surface disturbances, the additional disturbance required to construct ditches and
<br />sedimentation ponds to intercept, route, and treat runoff from thickener underflow pad and road areas, is not warranted.
<br />Similarly, for the associated temporary linear pipeline disturbances, construction of ditches and ponds to control runoff
<br />is impractical. Much of the EMD Thickener Underflow Pipeline disturbance will drain naturally to existing
<br />Sedimentation Ponds E, F, and G, and the majority of the drainage from pipeline areas is effectively isolated from the
<br />nearest drainage (Foidel Creek) by the existing raised railroad bed. The proposed BMP's have proven effective in
<br />controlling runoff and sedimentation from similar disturbances. Special design, construction, and operational measures
<br />have been incorporated in the design plans to assure that there will be no discharge or mixing of mine water with
<br />surface drainage.
<br />Following installation of appropriate ASC's for each portion of the project disturbance, available soil materials will be
<br />bladed from any new disturbance areas and temporarily windrowed or stockpiled on the upgradient edge of these
<br />disturbance areas. Much of the pipeline excavation and borehole pad disturbance will occur in areas that are, or have
<br />previously been, disturbed. For the remaining pipeline trench areas, consideration of soil horizon segregation must be
<br />balanced with the objective of limiting overall surface disturbance. In the interest of minimizing overall surface
<br />disturbance, TC proposes to not segregate and separately stockpile individual soil horizons for the pipeline trench
<br />disturbance, and submits that this approach will not significantly alter soil suitability characteristics, since the
<br />differences between the soil horizons is not significant over the areas to be affected by trenching. For the borehole
<br />drill -pads, individual soil horizons will be segregated, if present. Generally, to avoid contamination of the windrowed
<br />soil material, excavated material will be temporarily placed on the opposite side of the disturbance area.
<br />For the pipeline disturbance, the excavated trench will be backfilled and regraded as the pipeline is placed, with
<br />backfilling lagging behind pipeline placement consistent with pipeline fusing and installation requirements. Soil
<br />materials will be replaced following completion of pipeline installation. Reseeding of the disturbed areas will be
<br />completed during the first appropriate planting period following soil material replacement. When no longer needed
<br />to support ongoing or future mining and related operations, the thickener underflow boreholes and associated pads
<br />and roads will reclaimed by removing the surface manhole structures, plugging and sealing the boreholes consistent
<br />with State Engineer requirements, cutting -off the casings below ground level and placing a permanent marker,
<br />removing surfacing material from pads and roads, regrading the pads and road areas to blend with the surrounding
<br />terrain and reestablish drainage, replacing soil materials, and reseeding with the appropriate approved seed mix for
<br />the associated disturbance area(s). Pipelines will be abandoned in-place, with the ends of the pipelines cut-off and
<br />capped below grade.
<br />18LT Mine Water Transfer Pipeline (TR09-70) - As a limited, temporary, surface disturbance, construction of the
<br />i 8LT Mine Water Transfer Pipeline will have minimal impacts on surface water hydrology, relative to runoff and
<br />sediment contributions. It is anticipated that a maxinnun of 300 feet of pipeline trench will be open at any given time.
<br />Soil removal and windrowing from this limited pipeline construction area will create a shallow (approximately 1.0 foot
<br />deep) depression that, along with the trench excavation, will tend to contain any runoff from direct precipitation, as well
<br />as any minor amounts of run-on from adjacent areas. Where pipeline construction approaches Fish Creek or minor
<br />ephemeral/intermittent drainages, the specific BMP's and general protective measures previously detailed for the 18LT
<br />Pipeline, and outlined for pipeline disturbances will be utilized to control surface runoff and sediment. Surface
<br />disturbance areas associated with pipeline construction will be reclaimed concurrently with ongoing pipeline
<br />construction, and regraded surface areas will be left in a roughened condition, to control runoff and erosion, until they
<br />can be seeded. As a very limited disturbance area (a maximum of approximately 300 ft x 40 ft, or 0.28 acres) the active
<br />pipeline construction areas meet the applicable criteria for a Small Area Exemption, and construction of full-scale
<br />drainage and sediment control structures is neither needed nor justified.
<br />19RT Mine Dewatering Borehole and Pipeline (TRIO -73) - During construction, and for the minor surface structures
<br />that will remain during mining, drainage and sediment control for the 19RT Mine Dewatering Borehole and Pipeline
<br />will be provided by Alternative Sediment Controls (ASC's) consisting of combined Best Management Practice (BMP)
<br />measures. BMP's for the construction activities include:
<br />• Minimizing the area of surface disturbance
<br />• Scheduling of construction activities during the dry summer period
<br />• Placement of staked straw wattles downgradient of all surface disturbance areas to intercept any surface runoff
<br />and trap associated suspended solids
<br />TR 17-87 2.05-84.8 03/14/17
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