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<br />MR24-325 2.05-84.11a 03/27/24 <br />diversion ditches will drain through rock sediment basins to the undisturbed adjacent lands, and pad cut/fill areas will <br />be stabilized with temporary revegetation seeding. The total disturbance area will be less than 1.5 acres and meets the <br />applicable criteria for a Small area Exemption, the proposed drainage control measures should be effective in controlling <br />runoff and sediment. <br /> <br />6 East Utility Borehole (MR24-325) If the 6East Utility Borehole is needed and constructed the pad and access road <br />will involve limited surface disturbance required for the pad and access road. With limited run-on from the small <br />upgradient drainage area, the site drainage controlled will be addressed through a Small area exemption. Runoff and <br />sediment from the pad and road will be effectively controlled by gravel surfacing, revegetation of cut/fill areas, and <br />downgradient sediment control for the soil stockpiles. The upgradient diversion ditches will drain through rock <br />sediment basins to the undisturbed adjacent lands, and pad cut/fill areas will be stabilized with temporary revegetation <br />seeding. The total disturbance area will be less than 3 acres for the road and pad site and meets the applicable criteria for <br />a Small area Exemption, the proposed drainage control measures should be effective in controlling runoff and sediment. <br /> <br />Field Geotechnical Investigations – TC occasionally conducts field geotechnical investigations prior to, and as the basis <br />for, design and construction of engineered structures. Geotechnical investigations typically involve shallow soil borings <br />(up to 30 feet) using a hollow-stem auger, and/or excavation of shallow (up to 15 feet) test pits. For both soils borings <br />and test pits, surface disturbance is minimal (no more than 10 x 10 feet for boreholes, and 10 x 15 feet for test pits) <br />and both disturbance and subsequent stabilization occur within a timeframe of less than one day for each site (typically <br />test pit excavation/soils boring, and backfilling and leveling of the resultant small area/auger-hole, occurs in a <br />continuous sequence within the course of less than two hours for each location). The geotechnical investigation <br />activities do not involve the use of water and are conducted under dry conditions, so the potential for related <br />hydrologic impacts is negligible. All geotechnical disturbance is reseeded by broadcast seeding within 6-months of <br />disturbance, although natural revegetation typically occurs much sooner due to the limited timeframe and extent of <br />the associated disturbance. Occasionally perforated PVC pipe may be inserted in a completed borehole, and the <br />remainder of the hole backfilled with clean gravel, as a temporary piezometer installation to measure any fluctuation <br />in water-levels. This type of piezometer installation is normally very temporary (typically used less