1996-01-26_GENERAL DOCUMENTS - C1980007

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c. Surface Water The North Fork of the Gunnison River is the major drainage for the mine area. Smaller streams in or adjacent to the life-of-mine areas are all tributary to the North Fork. Figure 1 of this document contains the drainage map of the study area with the locations of streams and reservoirs which are described in the following discussion. The North Fork has an average annual streamflow at Somerset of approximately 313,500 acre-feet per year (1962-1979). The flow is regulated by the Paonia Reservoir on Muddy Creek five miles upstream of the town of Somerset. The reservoir became operational in 1962. Water yields during that period have ranged from a high of 601,800 acre feet per year in water year 1984, to a low of 82,270 acre feet in water year 1977. Flow records for the North Fork of the Gunnison River near Somerset are given in Table 1 of this document. Water quality parameters for the North Fork are given in Table 2 of this document. As indicated, water in the North Fork is a calcium bicarbonate type. There are also moderate levels of sulfate and salinity averages less than 100 mgll. The West Elk mining operation is adjacent to Sylvester Gulch, Lone Pine Gulch, and Gribble Gulch, which are ephemeral streams that flow directly to the North Fork. No flow has been observed in Lone Pine Gulch for a period of several years. Sylvester Gulch has a drainage area of 4.25 square miles. The hydrologic yield of Sylvester Gulch is low compared to the other watersheds in the West Elk life-of-mine area. This is due to the fact that it drains an area which is lower in elevation and has gentler slopes. Monitoring of Gribble Gulch, which could potentially be impacted by mining in Jumbo Mountain, began in September 1993. Most of the West Elk Mine underlies the Minnesota Creek drainage to the south. The Minnesota Creek basin is a significant drainage system occurring in the :southern part of the five-year permit area, and within the life-of-mine coal lease boundary. Minnesota Creek and its tributaries drain the southern portion of the coal lease area. These tributaries include Horse Creek, South Prong, Lick Creek, Dry Fork, and East Fork. Minnesota Creek enters the North Fork of the Gunnison near Paonia. The Minnesota Creek drainage extends approximately 53.5 square miles as shown in Figure 2 of this document. The West Elk life-of-mine area is drained by five tributaries to Minnesota Creek. These tributaries include East Fork, Horse Creek, South Prong, Lick Creek, and Dry Fork. Characteristics of the drainages are given in Table 3 of this document. Lick Creek and Dry Fork average slopes are generally steeper and the watersheds are at higher elevations than 26