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-46- Cumulative Hydrologic Impact Assessment - Surface Water (COnt'd) The Mt. Gunnison application has proposed a subsidence protection plan for the Dry Fork of Minnesota Creek to protect .streamflow. The adequacy of this protection plan was not assessed as a part of the .1RC0 permit review (this area lies outside of the current, 5-year permit area). The Division stipulated that site-specific monitoring data concerning subsidence and its hydrologic effects be taken into account in the design of any protection plan. Three perennial streams cross the southern portion of the l7t. Gunnison life-of-mine area; Lick Creek, South Prong, and Horse Creek. Subsidence effects could be significant along these stream courses as well, unless the applicant undertakes to design subsidence protection plans for these drainages as well as Dry Fork. L~pletion of Seeps and Springs Underground mining, even in the absence of subsidence, could cause flow from inter- mittent and perennial springs to be depleted, or even to go completely dry. The significance of this effect depends upon the use of the spring water and its contribution to flow in receiving streams. Underground mining at the Mt. Gunnison !?ine has a high potential for affecting springs located in Sylvester Gulch. However, flow from these springs is already diverted into the Tony Bear Pipeline for use in the Bear mining operation, and does not reach the North Fork of the Gunnison. The lit. Gunnison permit application identified numerous springs in or adjacent to the area to be mined. The application indicates that springs contribute 11 percent of the flow in Lower Dry Fork, 9 percent of the flow in Lick Creek, 12.6 percent of the flow in South Prong, and 0.9 percent of the flow in Horse Creek. Excluding the Sylvester Gulch data, springs could contribute 6.2 percent of the stream flow for the life-of-mine area during the dry part of the year. In a worst- case scenario, where all of the springs dry up, 6.2 percent of the Iorr flow runoff could be lost. In reality, it is probable that not all the springs would be affected and, therefore, reduction of surface flow, although significant, would be less than the worst-case scenario. A loss of springflor/ is not entirely lost to the hydrologic system. It would tem- porarily become a part of the ground water system and would eventually reemerge to the surface. Tt is difficult to predict where this water would reemerge. It could reemerge downstream in the same drainage (the Minnesota Creek system), or it could reemerge along the North Fork of the Gunnison. In the Later case, the impact upon water users located along Minnesota Creek is potentially the greatest. In either case, flow below the confluence of Minnesota Creek and the North Fork of the Gunnison should not be affected. Withdrawal of Water from the North Fork of the Gunnison for Mine Use Streamflows may also be depleted through the withdrawal of water from the stream or the alluvium of the stream for use in the mining operations.