Laserfiche WebLink
-9 - <br />The permit revision for the Hayden Gulch Mine has been reviewed by the <br />Division to determine whether changes to the originally projected hydrologic <br />consequences and cumulative impacts of mining in the area would be required <br />under the projected changes contained in the permit revision. The Division <br />has determined that the projected changes to the mine plan do not <br />significantly affect the projections and conclusions in the probable <br />hydrologic consequences analysis and the cumulative hydrologic assessment. <br />A significant factor with respect to hydrologic consequences is related to the <br />quantity of ground and surface water in the permit and adjacent areas. <br />Surface water flow within the drainages which will be affected is sporadic and <br />occurs primarily in response to periods of snowmelt or individual rainfall <br />events. <br />Some of the flow will be removed from Hayden Gulch as a result of containment <br />within the sediment control system and will be consumed by the operation (dust <br />suppression). Surface water in Dry Creek and Dowden Gulch will also be <br />impacted by the operation. The area removed from the Dry Creek drainage as a <br />result of a diversion around the spoil pile is insignificant with respect to <br />the total drainage area of the Dry Creek basin. <br />Flow in Dowden Gulch will not be impacted under the proposed revision, since <br />mining will not extend into Dowden Gulch. <br />The load-out occupies a relatively small portion of the Dry Creek drainage. <br />All runoff will be contained within the sediment control system and will be <br />treated prior to release. The effect on surface water quantity in Dry Creek <br />as a result of the operations at the load-out is negligible. <br />The effect of the operation on surface water quantity will be greatest during <br />the mining and reclamation stages. Once the areas are reclaimed, the sediment <br />ponds will be retained as stock ponds. All other aspects of the surface water <br />hydrology will return to pre-mining conditions (i.e., post-mining topography <br />and drainage, etc.). <br />During the operation, a few water-bearing strata will be impacted. Most these <br />strata are within the area mined. Some springs originating in localized <br />sandstones may also be impacted. In many instances, the strata within the <br />mined area were dry according to static water level measurements (p. 24, <br />Section 4, Appendix R, Volume VII). Measurements of discharge from the <br />springs indicate that water yield is low from these strata. Most of the <br />ground water usage in the surrounding area consists of registered wells that <br />are along strike or updip of the mine and which, in many cases, are <br />hydrologically isolated from the mined area. The only well downdip of the <br />mine is too far from the disturbance to be affected. <br />Degradation of surface water quality will be minimal during the operation. <br />Runoff from all disturbances will be contained within a sediment control <br />system. Water quality will be periodically monitored upstream and downstream <br />of the sites to determine impacts of the operation. Any discharges from the <br />sediment control system will have to meet minimum quality standards. <br />Successful reclamation of the disturbance will nearly restore baseline <br />conditions. <br />