2021-04-28_PERMIT FILE - C1981008

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Site Specific Surface Water Information Drainase Basin Geomorphology The New Horizon 1 mine is located on the gently sloped upland just north of Tuttle Draw, in the southern portion of the Second Park. The New Horizon 2 mining area includes the mildly sloping upland area between Tuttle Draw (to the north) and Calamity draw (to the south). The area is located approximately in the middle of the First Park. Both the First and Second Parks are relatively flat (gently sloping) areas formed by regional uplift of sedimentary rocks that have been subsequently dissected by both Tuttle and Calamity Draws. Both Parks consist primarily of recent deposits of undifferentiated eolian silts and sands that overlay the Dakota and Burro Canyon Formations. With the completion of the Colorado Cooperative Company's Main Irrigation Ditch in about 1910, these deposits have been intensively reworked by cultivation using irrigation water to form a broad rolling valley across the First and Second Parks. The New Horizon 2 permit area is located in the water sheds of both Tuttle Draw and Calamity Draw. The permit area to the south and east of the West Lateral irrigation ditch drains into Calamity Draw and consists of 396 acres. The area north and west of the West Lateral irrigation ditch drains into Tuttle Draw and consists of 412 acres. The drainage area of Calamity Draw to its confluence with the San Miguel River is about 7.0 square miles. The drainage basin of Tuttle Draw is about 16 square miles. With the exception of the lower portion of the Calamity Draw basin (near the mouth), the watershed is largely comprised of irrigated pasture and rangeland (First Park) and to a lesser extent, the townsite of Nucla, Colorado. The middle and upper portions of Calamity Draw Basin have been intensively irrigated and cultivated since the early 1920's and late 1910's. The development of the townsite and corresponding spread of cultivated and irrigated fields has resulted in a disjoint tributary drainage pattern almost completely controlled by the return ditches of the irrigation network. These return ditches (tributaries) in the mid- and upper portion of Calamity Draw are mostly intermittent and possibly perennial and are largely influenced by the timing and application of irrigation water. The overall average basin slope of Calamity Draw is about 76 feet per mile, with an average basin elevation of 5,857 feet above MSL. For the basin area in Calamity Draw above the location of surface water monitoring Site SW -N103 (see Map 2.04.7-1A Hydrologic Monitoring Site Location Map), the average basin slope is approximately 48 feet per mile. This suggests that since the onset of man's activities in the upper portions of Calamity Draw (cultivation of land and the establishment of the townsite), these activities have greatly influenced the basin geomorphology of this watershed. The Tuttle Draw drainage consists of both non -irrigated grazing areas and irrigated cultivated land. The drainage area above Nucla and the intersection of the Second Park irrigation ditch and the West Lateral irrigation ditch is non -irrigated range land developed on the more steeply dipping slopes of the southwest flank of the Uncompraghre Uplift. Tributaries to Tuttle Draw in this area incise the dip slopes resulting in local topographic relief of up to 200 feet (Spradlin Park area). This produces a moderately sloping rough mesa and canyon topography in this area with the mesa tops (dip slopes) sloping to the southeast at about 320 feet per mile. Below Nucla and the intersection of the two irrigation ditches, slopes are more moderate and the flatest land is irrigated. Tributaries to Tuttle Draw along the northern flank of First Park typically have local topographic relief of 100 feet or less. The mesa to the south of Tuttle Draw located in the revised New Horizon 2 permit area slopes generally to the west at about 130 feet/mile. The lower reaches of Tuttle Draw are steeper. Topographic relief at the mouth of Tuttle Draw is about 300 feet. The Tuttle Draw drainage area encompasses elevations from 6580 feet to 5240 feet with an average gradient of about 140 feet/mile. The stretch of Tuttle Draw that drains to the revised New Horizon 2 mine permit area has a gradient of about Page 2.04.7-17 March 2017 (TR -77)