1988-04-11_PERMIT FILE - C1981008A (23)

Home Browse Search

Alluvial Valley Floors Introduction. At the request of the CMLRD, Peabody submitted, on November 17, 1980, a report entitled "Reconnaissance Investigation for the Identification of Potential Alluvial Valley Floors in the Vicinity of the Nucla Mine". The reconnaissance area included those portions of Tuttle and Calamity Draws which are adjacent to or near the Nucla Mine. The San Miguel River was not taken into consideration. However, CMLRD undertook a study in 1983 to determine if the San Miguel River could be considered a potential alluvial valley floor where it runs adjacent to the Nucla Mine. The results of that study determined that there was a sufficient distance separating the mine from the San Miguel River to mitigate any impacts that may occur. Refer to the CMLRD's Nucla Mine Proposed Decision and findings of Compliance Document (1983) for the results of their study. The discussion that follows is based on information contained in Tab 7, field observations, and interpretation of false-color infrared and color aerial photographs at scales of 1" = 5001. Geomorphology. The areas (First and Second Park) in which the Nucla Mine and the proposed Nucla East mining area are situated were formed by a regional uplift of sedimentary rocks with the uppermost strata being the Cretaceous Dakota sandstone and Burrow Canyon formations. The formations are overlain by varying thicknesses of undifferentiated eolian silts and sands. These deposits have subsequently been reworked by water, forming rolling upland valleys that are dissected by both Tuttle and Calamity Draws. Since completion of the Colorado Cooperative Company's main irrigation ditch around 1910, the unconsolidated deposits have been further reworked by man to form broad rolling valleys across the first and second park, making the area more conducive for irrigation and agriculture. Nucla Mine is located on a gently sloped upland area on the north flank of Tuttle Draw in the southern portion of the Second Park. It is situated entirely within the Tuttle Draw Watershed (14.5 square miles). Tuttle Draw watershed is an upland drainage area that is tributary to the San Miguel River, consisting primarily of pinyon-juniper woodland and mountain scrub/brush types of vegetation. The portion of the watershed that lies in the Second Park area is mostly irrigated pasture and Sagebrush rangeland. The watershed has a dendritic drainage pattern with steeply incised ephemeral side tributaries, except for areas in the vicinity of irrigation, which intermittently carry irrigation return water. Tuttle Draw near the Nucla Mine is a meandering perennial stream (due to irrigation 16-11 Revised 04/11/88