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West Elk Mine <br />• "Protection of Hydrologic Balance" and Section 2.05.6 (6)(e)(i)(D) - "Detailed Description of <br />Predicted Subsidence Phenomena". Additionally, MCC has a decreed augmentation plan for <br />Minnesota Creek (Exhibit 52), which protects vested water rights from injury should the water <br />supply be adversely affected. <br />The other location of possible alluvial deposits within the mine pemut azea is within the west <br />branch of Sylvester Gulch as shown on (on map 66). The Sylvester Gulch Valley widens slightly <br />in this location and there is a sharp break in slope from the valley sides. However, the alluvial <br />origin of the valley deposits at this location is doubtful. The soils are a deep clay Arquistolls. <br />They are susceptible to mass movement and are typically found on side hill locations <br />(Reconnaissance Soil Survey, West Elk Study Area, 1976). The lack of base level control that <br />would favor clay deposits in this reach of Sylvester Gulch suggests that the valley deposits are of <br />glacial or perhaps colluvial (mass movement) origin. <br />The flood irrigation potential of the site is also questionable. Stream flow records neaz the mouth of <br />Sylvester Gulch indicate that flow during the critical months of July and August aze not common. <br />Agricultural development would be limited to grasses and pasture because of the elevation and <br />short growing season. <br />Outside the permit azea, but within the reconnaissance investigation azea, there aze two general <br />azeas of alluvial deposits. One is along the North Fork of the Gunnison River, and the other is along <br />Minnesota Creek and the East Fork of Minnesota Creek. The alluvial valley deposits aze wider and <br />contiguous where the streams leave the narrow canyons. Agricultural development is evident on <br />these lower valley fills. Isolated hay meadows aze also found fiuther up in the narrow valley of the <br />East Fork of Minnesota Creek. However, as one moves up the East Fork, these azeas become more <br />isolated and were not found above the 6,800 ft. elevation. <br />Map 66 delineates those areas along the main stem of Minnesota Creek where agricultural activities <br />aze supported by irrigation or flood irrigation. For the purposes of this evaluation, mapping was <br />stopped at the west section line of Section 2, T14S, R91 W, a point over two miles from the permit <br />boundary and downstream of the headgates of the Turner Ditch and Minnesota Ditch. During low <br />flows (i.e., irrigation demand periods) these two ditches effectively dry up Minnesota Creek. Below <br />this point return flow utilization, if any, is the water source for activities during low flows. <br />Map 66 was originally developed in 1984. The map has been put into electronic format using the <br />standard mine base mapping. In addition, the agricultural areas have been remapped in 2005 as part <br />of the South of Divide permit revision. There aze no alluvial valley floors in the South of Divide <br />permit azea. As shown on Map 66, the only alluvial valley floors in the vicinity aze located <br />downstream of mining activities. The only way for mining activities to affect the alluvial valley <br />floors is indirectly by changes to water quality and quantity. The section entitled "Protection of <br />Hydrologic Balance - 2.05.6(3)(a-c)" addresses these issues. Similarly, monitoring for possible <br />impacts to alluvial valley floors is accomplished by the water quality monitoring program for the <br />permit azea. <br />• In the azea where irrigation is used, the flow regime of Minnesota Creek is totally controlled by a <br />series of reservoirs and diversion ditches. Beaver Reservoir effectively regulates spring runoff on <br />2.065 Revised lrsrse 2005 PRIG; Rev. March 2006 <br />