2009-06-02_PERMIT FILE - C1982056A (4)

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Much of the pipeline excavation and borehole pad disturbance will occur in areas that are, or have previously been, disturbed. For the remaining pipeline trench areas, consideration of soil horizon segregation must be balanced with the objective of limiting overall surface disturbance. In the interest of minimising 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. Generally, to avoid contamination of the windrowed soil material, excavated material will be temporarily placed on the opposite side of the disturbance area. BMP's for the construction activities include: • Minimizing the area of surface disturbance • Installation of the Foidel Creek crossing as a bored/jacked pipeline under the existing Foidel Creek road crossing culverts (avoids new surface disturbance of the stream channel and floodplain) • Completion 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 riparian seed mixtures (as appropriate) immediately following completion of construction activities Where pipeline disturbance traverses steep slopes, additional staked straw wattles will be placed on contour to limit overland flow following revegetation seeding. Temporary drainage and sediment control measures will remain in-place until vegetation is sufficiently established to effectively control runoff, erosion, and sediment loss. Drainage and sediment control for the 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. As a relatively small (0.6 acres) linear surface disturbance, the additional disturbance required to either construct or intercept and route runoff from the disturbed area to a sedimentation pond is not warranted. The proposed BMP's have proven effective in controlling runoff and sedimentation from similar disturbances. Special design, constnzction, and operational measures were taken to assure that there will be no discharge or mixing of mine water with surface drainage. These measures include buried placement (approximately 5 feet below grade) of the Thickener Underflow Pipelines within a secondary containment pipe within and in proximity to the Foidel Creek drainage, and installation of differential pressure gauges, pump controls, and shut-off valves to provide for timely detection, shut-off, and isolation of the pipeline in the event of pipeline leakage. Field Geotechnical Investigations -TCC occasionally conducts field geotechnical investigations prior to, and as the basis for, design and construction of engineered structures. Geotechnical investigations typically involve shallow soil borings (up to 30 feet) using ahollow-stem auger, and/or excavation of shallow (up to 15 feet) test pits. For both soils borings and test pits, surface disturbance is minimal (no more than 10 x 10 feet for boreholes, and 10 x 15 feet for test pits) and both disturbance and subsequent stabilization occur within a timeframe of less than one day for each site (typically test pit excavation/soils boring, and backfilling and leveling of the resultant small area/auger-hole, occurs in a continuous sequence within the course of less than two hours for each location). The geotechnical investigation activities do not involve the use of water and are conducted under dry conditions, so the potential for related hydrologic impacts is negligible. All geotechnical disturbance is reseeded by broadcast seeding within 6- months of disturbance, although natural revegetation typically occurs much sooner due to the limited timeframe and extent of the associated disturbance. Occasionally perforated PVC pipe may be inserted in a completed borehole, and the remainder of the hole backfilled with clean gravel, as a temporary piezometer installation to measure any fluctuation in water-levels. This type of piezometer installation is normally very temporary (typically used less than a month) and will not impact groundwater due to the shallow depth and use of natural cuttings as backfill. Any piezometer installations are reclaimed by either pulling the PVC pipe and placing additional fill, or plugging the PVC pipe in-place using bagged bentonite grout, then capping the installation with a minimum 1.5-foot surface plug of natural clays or cement with a site marker. 18-Left Ventilation Shaft Installation (TR09-66) Approximately 420 feet of the light-use road crosses upland areas, where road construction will involve removal of any large vegetation and stripping and stockpiling of other vegetation, soil, and organic materials. Similarly, the TR09-66 2.05-84.6 04/11/09