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'• for domestic purposes is estimated to average about 1.0 acre-foot, and monthly demands should be fairly constant. For 1991-93, the domestic use at the Seneca II-W Mine averaged ' 0.64 acre-foot annually and ranged from 0.43 acre-foot to 1.05 acre-feet. The return flows from the domestic uses will accrete to a tributary of Grassy Creek and will be about 90 percent of the use or 0.9 acre-foot annually. The industrial component will include water used for dust suppression, evaporation from ponds, and incidental purposes. The water demands for industrial purposes are estimated to be 40.0 acre-feet annually. At the Seneca II-W Mine, the water use averaged 23.4 acre-feet annually for these purposes during 1991-93. The estimate for the Yoast Mine is larger than the actual use at the Seneca II-W Mine because the Yoast Mine includes a 3-mile ' long haul road to the county highway. The monthly water use at the Yoast Mine should be proportional to the water use at the Seneca II-W Mine. The average monthly use for 1991-93 as a percentage of the annual use at the Seneca II-W Mine ranged from 0.1 percent in January to 22.9 percent in June. The monthly water demands for the Yoast Mine are shown in Table 1. ' SCC will construct 2 water supply/sediment detention ponds known as Ponds 010 and 012. These ponds are shown on Plate 1. The ponds will store and decant intercepted ground water from the mine areas and surface water runoff. The net evaporation from the ponds was ' estimated to average 26.46 inches annually and to range from zero during December through February to 5.40 inches in July. The combined maximum water surface area of the ponds will about 5.0 acres. If the ponds are kept full year round the net evaporation will total about 11.06 acre-feet annually. The derivations of the monthly evaporation rates are shown in Table 2 and the monthly net evaporation volumes for the ponds are shown in Table 1. ' SCC also will construct 3 sediment detention ponds, known as Pond Nos. 011, 013, and 014, which will intercept and decant intercepted ground water from the mine areas and surface water runoff. The structures will decant the sediment and pass or release the water. The detention time will be short and evaporation losses will be insignificant. These ponds are ' shown on Plate 1. ' Water Sources A well, referred to as the "Yoast Mine Shop Well", will provide the water supplies for ' the domestic water uses and will supplement the surface water supplies for the industrial uses. The well will be developed in the Trout Creek Sandstone and will be located in the NW%. NE'/. of sec. 8, T.5 N., R.87 W. as shown on Plate 1. The volume of water provided ' by this well for industrial purposes will be inversely related to the volume of surface water available at Ponds 010 and 012. In other words, SCC will use the well for industrial purposes only when surface water supplies are inadequate. Accordingly, the well pumpage could range ' from 1 to 41 acre-feet annually depending on the surface water supplies. In a similar arrangement, the well pumpage at the Seneca II-W Mine ranged from 2.8 acre-feet in 1993 to 17.1 acre-feet in 1992. r Pond 010 will be located on an unnamed tributary of Scotchman's Gulch and Grassy Creek in the NW %. NE%a of sec. 8, T.5 N., R.87 W. The drainage area at this site totals about 1 .4 square miles. The storage capacity will be about 19.5 acre-feet and the maximum water surface area will be about 2.5 acres. ' 2