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was not of sufficient volume to cause any channel alterations, downcutting, or side- <br />cutting. <br />The Division is not aware of any impact to the City of Rockvale water line at the haul <br />road crossing. Any interruption of this pipeline due to mining would be a serious <br />consequence to city water users. The pipeline remains intact and functional to the <br />knowledge of the Division. <br />Surface water can be impacted by mining and subsequent subsidence. Perennial and <br />intermittent streams can be captured by surface cracking caused by subsidence, <br />especially in areas of shallow cover. Anecdotal and visual evidence suggests that <br />South Oak Creek flows normally in response to storm events and snowmelt in the <br />spring. <br />Mine water discharge, in large volume, could impact irrigation waters downstream of <br />the mine. An irrigation takeout exists 500 yards downstream of the confluence of <br />Lewis Gulch and Oak Creek. If waters discharged were of moderate to poor quality <br />and high in dissolved solids, irrigation waters in Oak Creek could be affected. Due to <br />the limited amount of mine water discharge and the relatively good quality of this <br />water, no impact to irrigation water would occur, especially considering the dilution <br />potential of the natural waters in Oak Creek. <br />Seepage of degraded ground water could also impact surface water over time as <br />ground water migrates to the natural discharge point. In the case of the Twin Pines <br />No. 2 Mine, the Brookside coal seam outcrops above Oak Creek and is not in direct <br />contact with the stream system, nor would any discharge be expected to reach the <br />stream in sufficient quantity to cause a problem. <br />Two former sediment ponds remain as permanent impoundments at both the portal <br />area and the coal sales yard. Any surface runoff from the two reclaimed areas would <br />be limited to snowmelt or rainfall runoff. Vegetation appears to be successful in <br />stabilizing the soil profile assuming proper land management practices. In the event <br />of any minor erosion occurring in the future, significant sediment treatment capacity <br />remains in the two permanent ponds. Any discharge of water would likely be treated <br />to an equal or better condition as compared to runoff from surrounding and adjacent <br />lands. <br />Findings on Protection of Hydrologic Balance <br />Based on the discussion provided above for surface and ground water impacts, the <br />Division finds that the Twin Pines No. 2 Mine has minimized disturbance of the <br />hydrologic balance in the mine plan and adjacent areas, and has prevented material <br />damage outside the permit area. The Division also finds that the Twin Pines No. 2 <br />Mine has not caused hydrologic changes that adversely affect the approved post- <br />mining land use in the permit area. <br />17