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IV. Topsoil — Rule 4.06 <br />April 3, 2012 <br />RN4 <br />waters. During an average year, runoff from the site is calculated to contribute <br />between 13 and 69 tons /day dissolved constituents as TDS which may not, however, <br />actually enter Naturita Creek or the San Miguel River. Infiltration, evaporation, and <br />evapotranspiration will reduce runoff, sometimes to nothing. As an extreme example, <br />in the low flow year 1977, when the San Miguel River at Naturita had a total flow of <br />1.6 cfs, it is possible that there was no flow from most or all of the drainages into <br />Naturita Creek, nor from Naturita Creek itself for an extended period of time. In the <br />case of a high precipitation event, the amount of dissolved constituents carried from the <br />site is expected to increase and the concentrations decrease as a direct result of the <br />increased volume of water after an initial flushing effect. <br />Runoff volumes of the area being worked during mining activities are expected to <br />increase somewhat due to compaction by equipment and exposure of materials with <br />higher clay and silt content than that currently at the surface. This effect is expected to <br />be offset by low precipitation, minor ponding of precipitation in the working area, <br />retention of runoff in the sediment ponds, evaporation and infiltration. Pit dewatering <br />was not required. TDS and other constituents of concern, sulfate in particular, are <br />expected to have minimal or insignificant effect on the water quality of the receiving <br />waters as the volume of the runoff will be extremely low. No material damage to <br />receiving waters is expected. <br />Post - mining contours and revegetation are expected to reduce runoff and erosion below <br />current conditions, thereby reducing potential impacts after reclamation. This <br />reduction will result from increased infiltration and evapotranspiration due to reduced <br />rates of overland flow during higher precipitation and snowmelt events, and increased <br />vegetative cover. Surface water monitoring will adequately characterize runoff quality <br />and quantity so that changes, if any, will be detected and potential impacts can be <br />analyzed. <br />An analysis of Probable Hydrologic Consequences of the Hamilton Mine has been <br />supplied with the application, in accordance with Rule 2.05.6(3). Any impacts that <br />may occur are not expected to impact the hydrologic balance of the area. The <br />operations as proposed have been designed to prevent material damage to the <br />hydrologic balance outside the permit area. Appropriate measures are outlined in the <br />application to ensure protection of surface and ground waters in the permit and <br />adjacent areas from adverse effects due to the proposed mining operations. <br />A. The Division waived the requirement for clearing of vegetation cover prior to topsoil removal in <br />most areas since the vegetation cover consisted of grasses, forbs and small shrubs. The applicant <br />has demonstrated that inclusion of vegetation cover in salvaged topsoil was necessary or <br />desirable to ensure soil productivity consistent with the post - mining land use. (4.06.2(1)). <br />V. Sealing of Drilled Holes and Underground Openings — Rule 4.07 <br />A. The applicant will ensure that each hole, well or other underground opening will be capped, <br />sealed, backfilled, or otherwise properly managed. (4.07.3). <br />18 <br />