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The Trout Creek alluvial aquifer roughly parallels the western boundary of the permit azea. Currently, the Trout Creek alluvial aquifer is monitored by three wells observing depth-to-.vaterand water quality trends above, adjacent to and below the mine site. Some degradation of the alluvial water quality has, and will continue to occur, as water moves from the spoils out into the alluvium. The fourth aquifer in the Edna Mine azea are the former pit azeas where, backfilled pits become spoils aquifers upon resaturation. Subsequently,whenthe elevation of the saturated portion of the spoils exceeds the topographic low point along the buried highwall, water is discharged at the surface in the form of springs. In fact, at the Edna Mine, ntunerous spoils springs and seeps have been identified adjacent to Trout Creek, dischazging water high in TDS and sulfates to the alluvial aquifers and directly to Trout Creek. Surface Water The permit area lies in the upper Yampa River basin and is drained by several ephemeral streams which flow into Trout Creek and Oak Creek -perennial streams flowing in a northeasterly direction toward the Yampa River. These ephemeral streams draining the permit area flow predominantly west-northwest into Trout Creek. Oak Creek flows along the eastern limit of the permit area but receives only a small portion of the runoff because the Trout Creek -Oak Creek drainage divide is very neaz the eastern boundary, in fact defining that boundary in places. Both perennial streams aze incised into bedrock, with Trout Creek draining approximately 54 square miles above the northern limit of the mine, Oak Creek approximately 32 squaze miles. Runoff events in both these streams aze dominated by snowmelt. Peak spring runoff occurs slightly later in Trout Creek than in Oak Creek because the headwaters of the former aze located at a much higher elevation. Mining operations facilities should not be significantly impacted by large flood events from these streams. The Trout Creek floodplain is well below proposed and existing mining activities. The loading facilities and office azea are adjacent to Oak Creek, but above the 100-year, 24-hour floodplain. Trout Creek forms the western boundary of the permit azea. The ephemeral streams which drain the permit area flow west or northwest into Trout Creek. Sediment ponds are located at the base of these tributaries above their confluence with Trout Creek. The disturbed area is 3,400 acres, or approximately 10 percent of the 54 square mile Trout Creek drainage basin. The average annual runoff in Trout Creek is 37,500 acre-feet. The mine azea is estimated to yield approximately 730 acre-feet of runoff annually, or about 2 percent of the total annual stream flow of Trout Creek above the mine. Annual mean minimum discharge is estimated at 10 cubic feet per second (cfs). Only a small area of mine-related disturbance drains into Oak Creek. Although no mining occurs within this watershed, the loadout, conveyor, access road, and office are situated within the Oak Edna Mine 6 permit R<newal No. J