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III IIIIIIIIIIIIIIII 999 STATE OF COLORADO Roy Romer, Governor DEPARTMENT OF NATURAL RESOURCES MINED LAND RECLAMATION DIVISION FRED R. BANTA, Director DATE: May 17, 1989 T0: Matthew S. Hayes FROM: J.M. Clayton RE: Mt. Gunnison No. 1 Mine, File No. C-80-007, Mid-Term Review Surface Hydrology General Hydrologic Characteristics The Mt. Gunnison No. 1 Mine's life of mine area consists of 14,341 acres, is located approximately ten miles east of Paonia, Colorado and is in Gunnison County. The general area that includes the permit area is mountainous with elevations ranging between approximately 6,000 feet near Somerset and 12,719 feet at the summit of Mt. Gunnison. The life of mine area ranges in elevations from 6,000 to 9,200 feet. The life of mine area lies within the drainage of the North Fork of the Gunnison River which is tributary to the Colorado River System. The northern portion of the permit area is drained by the ephemeral streams, Lone Pine and Sylvester Gulches. Minnesota Creek and its five tributaries, Horse Creek, South Prong, Lick Creek, Dry Fork and East Fork, drain the southern portions of the permit area. Horse Creek, South Prong and Lick Creek are considered perennial streams while Dry Fork and East Fork are classified ephemeral. Volume 1, Section 3.4.8 states that South Prong and Horse Creek are the only perennial streams, contradicting later statements claiming all three to be perennial. Lone Pine and Sylvester Gulches discharge into the North Fork of the Gunnison at the northern boundary of the permit area while Iinnesota Creek discharges into the North Fork at Paonia. The North Fork of the Gunnison River begins at the confluence of Anthracite and Muddy Creeks, approximately five miles upstream from the permit area. At the Idt. Gunnison No. 1 Mine site, water in the North Fork is classified as a calcium bicarbonate type with moderate levels of sulfate. Salinity levels average less than 100 mg/1. The North Fork had an average annual streamflow of 313,500 acre feet in the years 1962 through 1979. This flow is largely regulated by the Paonia Reservoir which became operational in 1962. For additional details of the water chemical parameters please reference Figures 2.5.5A through Figure 2.5.5D in Volume 1 of the permit application. The headwaters of streams occurring on the Mt. Gunnison No. 1 Mine study area are largely underlain by igneous rocks which are relatively resistant to dissolution. The lower reaches of these streams are underlain by sedimentary rocks which contribute increases in suspended solids as well as altering chemical composition. Minnesota Creek water quality data indicate that its 215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567