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-27- Description of Hydrologic Environmer:t - Surface Water Regime (Cont'd) Both the BZve Ribbon and the Somerset mines have surface facilities and underground workings within the Hubbard Creek dr~.iinage basin. During 1980, Hubbard Creek flows ranged from 3 cfs to 130 cfs with an average flow of 31 cfs. The estimated annual yield for Hubbard Creek was 24,700 acre-feet/year, or 80 of the total flow of the North Fork for the year 1980, measured at Somerset, Colorado. Water quality data for Hubbard Creek are presented in Tables 4a and 9b. In a spring survey conducted at the Blue Ribbon Pfine site, only one ephemeral spring was noted and mapped. This spring is located below the Blue Ribbon Mine bench. A survey of Water Rights records conducted by the State Water Resources Division for the Somerset Mine revealed that there are no adjudicated springs tributary to Hubbard Creek on or adjacent to the permit areas of the Blue Ribbon and Somerset mines. Three separate drainages are located within or adjacent to the Orchard Valley Mine; Terror Creek drains the eastern portion of the Life-of-mine area, and East and west Roatcap Creek drain the western portion. Stevens Gulch is an ephemeral drainage between the Terror Creek and Roatcap Creek drainage basins, and has a drainage area of 6.0 square miles. One other ephemeral drainage within the Orchard Valley life-of-mine area, Long Draw, drains an area of 1.5 square miles and flows into West Roatcap Creek. The entire Roatcap Creek system contains no alluvial deposits, due to the steep topography and overall drainage gradient. One irrigation ditch, the Overland Ditch, follows the topographic contours at the northernmost boundary of the Orchard Valley life-of-mine area. There are several springs and numerous ponds within the permit and hydrologically adjacent area of the Orchard Valley Mine. It appears that, from the data submitted to date, most of these springs and ponds are intermittent and depend upon seasonal precipitation and long-term weather patterns. The source of most of the springs appears to be related to landslide complexes, to faults and fractures, to areas of colluvium/alluvium where ground water has accumulated, or to the discharge points at the basal contact of the Rollins sandstone and lenticular sandstones of the Mesa verde Formation. The current Bear and Mt. Gunnison mining operations are adjacent to Sylvester Gulch and Lone Pine Gulch, which are ephemeral streams flowing directly to the North Fork. The Mt. Gunnison life-of-mine area is drained by five tributaries to Pli nnesota Creek. Characteristics of the drainages are given in Table 5. No flow was observed in Lone Pine Gulch for a period of years; thus, it was omitted from the study. Sylvester Gulch is an ephemeral stream and has a drainage area of 4.25 square miles. As indicated on Table 5, the hydrologic yield of Sylvester Gulch is low compared to the other watersheds. This is due to the fact that it drains a lower elevation area with gentle slopes. East Fork, Horse Creek, South Prong, Lick Creek, and Dry Fork drain into Minnesota Creek from areas to be undermined by the Mt. Gunnison No. 1 Mine. Their slopes are generally more steep and the watersheds are at higher elevations than those tributary to the North Fork. Based upon streamflows measured in water year 1978, the water yields from these drainages are nearly an order of magnitude greater than that of Sylvester Gulch.