Laserfiche WebLink
This findings document developed by the Division incorporates the findings <br />document developed in April, 1983 for the original application along with the <br />new findings for the Permit Revision No. 1 application. <br />Description of the Environment <br />The Nucla Mine permit area will encompass 426.6 acres, The topography is <br />gently sloping with a few small ridges and swales. Most of the land <br />surrounding the permit area is agricultural and is used primarily for <br />irrigated and non-irrigated farmland which produces alfalfa and pasture <br />grasses. Agricultural practices have been abandoned within the permit area. <br />The mine is located within the southeast portion of the Colorado Plateau. The <br />region is characterized by broad, fairly smooth surfaced plateaus and mesas <br />with gently dipping slopes dissected by steep canyons. Surface elevations at <br />the mine range from a high of 5,767 feet (MSL) in the northwest part of the <br />permit area to a low of slightly less than 5,672 feet in the southeast part of <br />the permit area along Tuttle Draw (see Exhibit 7-1 of the permit application <br />and the attached Index Map). Total topographic relief for the permit area is <br />about 95 feet. <br />Surficial geology in the area consists largely of consolidated sedimentary <br />rock of Cretaceous age Dakota Sandstone. A veneer of Quaternary <br />colluvial/alluvial material is present in the drainages becoming more <br />significant along the major streams in the area (Figure 2). <br />The upper two seams of coal within the Dakota Sandstone member are mined at <br />the site. In ascending order these are the Number 2 or Lower Dakota seam and <br />the Number 1 or Upper Dakota seam. <br />Due to the nature of the Dakota Sandstone in the permit area, discontinuous <br />aquifers are present in the overburden, coal, and underburden. These areally <br />limited aquifers are generally characterized by poor quality water. <br />Surface water draining from the Nucla Mine enters Tuttle Draw, a tributary of <br />the San Miguel River. The San Miguel is located in west-central Colorado and <br />is tributary to the Dolores River. streamflow in the San Miguel is a result <br />of snowmelt runoff from the Uncompahgre Mountains to the east and summer <br />thunderstorms within the watershed. Low elevation tributaries such as Tuttle <br />Draw contribute relatively small amounts of streamflow due to low <br />precipitation. Peak flows occur in late May to June and are related to <br />snowmelt. The lowest flow on record for the San Miguel above the mine at <br />Naturita, Colorado occurred during August of 1977 when streamflow completely <br />ceased. <br />Most of the baseflow in Tuttle Draw is the result of irrigation return flow. <br />The source of this irrigation water is the San Miguel River. The historic use <br />of Tuttle Draw has been identified as irrigation return flow for downstream <br />agricultural use. Water quality in the San Miguel tends to exhibit increased <br />total dissolved solids concentrations in late summer due to this use and lack <br />of available dilution water during this low flow period. <br />-5- <br />