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As the Wolf Creek mining area is reclaimed, the backfilled mining pits will, over time, resaturate. Spoil aquifers will develop and discharge to the surface system. A small portion of the spoil aquifer water will recharge the Wolf Creek Coal and overburden with water which is higher in TDS than the water which existed within the units previous to mining. The Wadge Coal and overburden units are potentially useful aquifers locally. Well yields for the Wadge Coal and overburden have been reported at between 2 and 5 gpm. In the vicinity of the Seneca II t4ine site, both units have been used for domestic and livestock purposes. The Wadge Coal has been mined in the northern portion of the permit area (Sand Wash Ground Water Basin) in the past. During the previous (1981-1986) and present (1986-1991) permit terms, the Wadge Coal is being extracted from the southeastern portion of the permit area, which is structurally located within the Twentymile Park Basin. The portion of Twentymile Park in which the Seneca II Mine is located has been identified as a recharge area. As such, the potential impacts of mining will be threefold: (1) Interruption of the aquifer by physically removing the coal and its overburden. Mining of the coal will interrupt the aquifer function upgradient of Twentymile Park. This will reduce the recharge potential to the down-gradient aquifer fora short period of time. (2) After discreet mining areas have been backfilled, the spoils will resaturate. A portion of the spoils water will recharge the undisturbed Wadge Coal and overburden immediately down-gradient. This recharge water will be high in TDS and other constituents. The concentrations of these constituents will be greater than that which existed in the Wadge Coal and overburden aquifer prior to mining. (3) It is thought that the Wadge overburden, through sub-crops and outcrops, may recharge creeks within Twentymile Basin. This recharge may be directly affected by the addition of the poor quality spoil discharge water during base flow conditions, or indirectly by the addition of this water to associated alluvial bodies. Recharge to the surface system could potentially be affected by the interruption of the aquifer due to removal by mining. Furthermore, upon indirect recharge by the spoils aquifer, a plume of poor quality water could diminish the water quality of the surface water system within Twentymile Park. The alluvial aquifer system, which includes alluvial bodies in the Fish Creek Drainage (including Bond and Cow Camp Creeks) and the Grassy Creek Drainage, will be impacted due to mining activities. During mining, surface runoff from the disturbed areas is contained in sediment ponds prior to discharging from the site. Historically, the sediment ponds at the Seneca II t4ine discharge regularly throughout the year to the associated drainages (Grassy Creek and Cow Camp Creek). These drainages, at -23-