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MR21-319 2.05-84.11a 07/27/21 <br />cut/fill areas, and downgradient sediment control for the soil stockpiles. With a limited disturbance area <br />(approximately 1.0 acres for the pad and 2.0 acres for the road) the disturbance areas meet the applicable criteria for a <br />Small Area Exemption, the proposed drainage control measures should be effective in controlling runoff and <br />sedimentation, and construction of full-scale drainage and sediment control structures is neither needed nor justified <br /> <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