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• known to occur rarely in areas with more than 300 feet of overburden. The B-seam mining would occur in locations with 400 to 1000 feet of overburden. Two special conditions of approval are recommended to protect unsurveyed cultural resources in the event that new subsidence or cultural resources information indicates that cultural resources may be affected by subsidence. The SHPO concurred with OSM's determination in a letter dated December 15, 1989, b. Water supply and quality values The probable hydrologic consequences of mining at the Mt. Gunnison No. 1 mine should not change in substance from the predictions made in OSM's November 1987 Environmental Assessment. Subsidence control plans should be sufficient to control adverse effects on Sylvester Gulch. While drainage patterns may be affected slightly in the permit area, subsidence is not expected to adversely affect surface flow in the ephemeral streams of the permit area. All drainage would continue to flow to the North Fork of the Gunnison River. There would be no changes to the drainage patterns of the Minnesota Creek watershed, nor any depletions of surface water flows in the Minnesota Creek watershed. • The worst-case depletion of springs and seeps discussed in OSM's November 1987 Environmental Assessment would not change due to the B-seam mining. The one additional spring that could be affected by B-seam mining produces less than 2 gpm. If affected by subsidence, the loss of surface flow to the North Fork of the Gunnison River would be negligible. WECC has committed to develop undeveloped springs to mitigate any loss of water from existing developed springs. Subsidence is expected to be minimal in the areas where the stockponds are located. The overburden is more than 800 feet thick. If subsidence does affect the viability of a stockpond, WECC has committed to replace or repair any ponds to mitigate any loss of water due to mining activities. Fracturing of strata above the B seam is expected to have minimal, if any effect on aquifers below the B seam. The only significant regional aquifer in the area (i.e., the Rollins Sandstone) is about 60 feet below the B seam and is virtually unused because of its depth. The strata between the B seam and the Rollins Sandstone consist of interbedded shales and sandstones that will effectively preclude infiltration of water below the B-seam mining area. B-seam inflows are projected to be about 15 gpm initially and 10 gpm on a long-term basis when production reaches 1.4 million tons per year. Inflows could triple to 11