GENERAL31521 - Laserfiche WebLink

Home Browse Search

r -46- The ground water assessment indicates that mining may affect several aquifers in the general area. The Trout Creek sandstone, Tow Creek sandstone, and Twentymile sandstone would not be affected by the Foidel Creek Mine. The Middle Coal Group aquifer may be affected by the Foidel Creek Mine, as well as by other mines in the area. During mining operations, ground water flow in this aquifer would be diminished. This effect is not significant because no wells are completed in this aquifer in the Twentymile Park Basin, and any loss of ground water contribution to surface streams is expected to be minor. Following mining and reclamation, ground water flows would return, but water of degraded quality may discharge to surface systems. This effect was included in the surface water model. Mining may affect the quantity and quality of flow in alluvial aquifers. Changes in water levels in the alluvium are not expected to be significant, and the expected water quality degradation would probably not limit pre-mining water uses. In lower Piiddle Creek, stream flaw and total dissolved solids concentrations would increase primarily as the result of discharge from the underground mine workings. Water from Middle Creek is used for irrigation. However, as shown on Map 14a, water is diverted upstream of the reach that would be affected by mining. The proposed Foidel Creek underground mine would have no adverse effect upon water use in this area. Water from Fish Creek is also used for flood irrigation. The model indicates that the total dissolved solids concentrations would exceed the use criteria (1000 mg/1) during the low flow months (August, September) of dry years. During these periods, the water in effected reaches of Fish Creek may be unsuitable for flood irrigation use. However, the actual effects would not be expected to be as great as the model predicts, In the model, the long-term effects of mining, primarily discharge of affected ground water, are directly added to surface flows. In reality, ground water discharge is to the stream/alluvial aquifer system. Flow in the alluvial aquifer would help to buffer the effects of mining. Both surface and alluvial ground water quality would be degraded, but surface flows would not be affected to the extent predicted by the model. Given the uncertainty in the prediction of long-tens effects, the water quality on Fish Creek is still within acceptable limits. However, it appears that affected water quality is approaching a total dissolved solids concentration beyond which water use may be limited. Lower Trout Creek and the adjacent Yampa River are used for both flood irrigation and domestic water. The projected effects of mining would not limit these uses. The cumulative hydrologic assessment indicates that, with the proposed hydrologic stipulations, the proposed mining operation has been designed to prevent material damage to the hydrologic balance outside the permit area.