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2.05.6(6) <br />change. Any gradient change will impact the stream characteristics. In an <br />extreme case, gradient changes may disrupt the flow. Such an event is not <br />probable in topographic conditions of the area where most stream channels <br />are relatively steep. Flow through the drainages could temporarily be <br />affected by a subsidence crack across a stream channel, however, the crack <br />would be expected to heal fairly quickly so the surface drainage pattern <br />would be naturally restored. <br />Very little flow has been recorded for the various ephemeral and intermittent <br />steams in the permit and adjacent area. These streams are expected to be <br />typically dry with flow occurring during spring snowmelt and after significant <br />precipitation events. Therefore, short term disruptions in the flow from these <br />streams should have very little impact on the water budget for Hubbard and <br />Terror Creeks. <br />Hubbard Creek, Terror Creek, West Terror Creek and the creek in Stephens <br />Gulch could be damaged by subsidence cracks which could cause surface <br />flow to run into the mine below. It may be possible to repair a stream that is <br />affected by a crack. First the flow interrupting crack would have to be <br />located. Then a culvert would be installed to divert the water from the crack. <br />Then the crack would be sealed with a impervious liner or other material. <br />Rockfall activity could damage and close roads and damage structures. The <br />structures at risk are the Operator's mine facilities. A large rock rolling into <br />one of the Operator's mine facilities could cause significant damage and loss <br />of life. <br />The sandstone ledge that forms Dove Cave will not be damaged since it is <br />not within the area to be affected by mining. <br />The water supply pipeline serving Pitkin Mesa may become disrupted or <br />separated due to strains induced by subsidence. <br />The WAPA transmission line that runs parallel along Terror Creek could be <br />very minimally impacted by subsidence. Potential subsidence could cause a <br />transmission tower to tilt slightly so it was out of plumb. <br />PR -14 2.05-154- 03/14 <br />