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of 2245 mg/1 from both Cow Camp Creek and Bond Creek. During August and September no flow in the tributaries is expected to reach Fish Creek as surface flow. There is no agricultural use of water immediately downstream of the Seneca II Mine on Grassy Creek. Due to the small quantity of flow contributed to the Yampa River by Grassy Creek, the increased concentration of TDS produced in the Yampa River would be minimal, and not preclude the beneficial uses of this water. An evaluation of the effect of increased TDS concentrations in Fish Creek is discussed in Section VII, Alluvial Valley Floors, of this document. Based on the foregoing analysis, the Division makes the finding that the Seneca II Mine site has been designed to minimize off-site surface water impacts. 2. Ground Water Both consolidated and unconsolidated aquifer systems have been identified at and near the Seneca II Mine site. These aquifers may potentially be affected by surface coal mining operations at this site. The Trout Creek Sandstone stratigraphically underlies the Wolf Creek Coal by 70 feet. The intervening strata, which consists of lenticular sandstone lenses, shale and siltstone has been identified as a confining layer in this area. This confining layer, which will not be actively disturbed by mining, will mitigate mining related impacts to the Trout Creek Sandstone. There will be no depletion or degradation of the water in this regional aquifer. The Twentymile Sandstone may be slightly impacted by the mining operation. The Bond Creek and Cow Camp Creek drainages bisect a Twentymile Sandstone outcrop adjacent to the southeastern portion of the permit area. The alluvial/colluvial material within each drainage will transmit water which has been discharged from spoils aquifers located upgradient in each drainage. This water, which is high in TDS, may recharge the Twentymile Sandstone at the point where the alluvial/colluvial material bisects the outcrop. The potential for water quality degradation due to potential recharge by the poor quality alluvial/colluvial water, is the only identified potential impact to this regionally significant aquifer. The Wolf Creek Coal, stratigraphically the lowest seam to be mined, as well as the associated overburden is capable of storing and transmitting small amounts of water, and at this location, may not meet the definition of an aquifer. Reported yields from wells completed in the Wolf Creek Coal are generally less than one gallon per minute (GPM1. Furthermore, high concentrations of iron, manganese and sulfate generally preclude use of this water for domestic or livestock use. The Seneca II Mine operation is removing the lJolf Creek Coal and overburden in the north central portion of the active mine area, which is located within the regional Sand Wash Basin. One consequence of mining will be the physical removal of this unit, thus interrupting recharge to the coal and overburden aquifer. _2P_