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Where pipeline disturbance traverses steep slopes, additional staked straw wattles will be placed on- contour to limit
<br />overland flow following revegetation seeding. Drainage and sediment control for the associated minor surface
<br />structures (borehole surface casings and any manhole(s)) will also utilize BMP's including the vegetative filter
<br />provided by temporary vegetative stabilization, and berms and/or wattles, as appropriate. The pad and access road for
<br />the 6RT Thickener Underflow Borehole installation have been designated as a Small Area Exemption (SAE), and the
<br />limited drainage from this area will be controlled by gravel surfacing, staked straw wattles, and
<br />reclamation/stabilization of the pad area following well installation. SAE designs for the 6RT Installation are provided
<br />in Exhibit 49S. Temporary drainage and sediment control measures will remain in -place until vegetation is sufficiently
<br />established to effectively control runoff, erosion, and sediment loss.
<br />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 hat 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, TCC 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 />Soil materials will be replaced following completion of pipeline installation. Reseeding of the disturbed areas will
<br />be completed during the first appropriate planting period following soil material replacement. When no longer
<br />needed to support ongoing or future mining and related operations, the thickener underflow boreholes will
<br />reclaimed by removing the surface manhole structures; plugging and sealing the boreholes, consistent with State
<br />Engineer requirements; cutting -off the casings below ground level, and placing a permanent marker; then
<br />regarding, replacing soil materials, and reseeding the associated disturbance areas. Pipelines will be abandoned in-
<br />place, with the ends of the pipelines cut -off and capped below grade.
<br />Field Geotechnical Investigations — TCC occasionally conducts field geotechnical investigations prior to, and as the
<br />basis for, design and construction of engineered structures. Geotechnical investigations typically involve shallow soil
<br />borings (up to 30 feet) using a hollow -stem auger, and/or excavation of shallow (up to 15 feet) test pits. For both soils
<br />borings and test pits, surface disturbance is minimal (no more than 10 x 10 feet for boreholes, and 10 x 15 feet for
<br />test pits) and both disturbance and subsequent stabilization occur within a timeframe of less than one day for each
<br />site (typically test pit excavation/soils boring, and backfilling and leveling of the resultant small area/auger -hole,
<br />occurs in a continuous sequence within the course of less than two hours for each location). The geotechnical
<br />investigation activities do not involve the use of water and are conducted under dry conditions, so the potential for
<br />related hydrologic impacts is negligible.
<br />All geotechnical disturbance is reseeded by broadcast seeding within 6- months of disturbance, although natural
<br />revegetation typically occurs much sooner due to the limited timeframe and extent of the associated disturbance.
<br />Occasionally perforated PVC pipe may be inserted in a completed borehole, and the remainder of the hole
<br />backfilled with clean gravel, as a temporary piezometer installation to measure any fluctuation in water - levels.
<br />_ -' This type of piezometer installation is normally very temporary (typically used less than a month) and will not
<br />TR09 -69 2.05 -84.7 10/23/09
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