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West Elk Mine <br />• The Oliver Mine, on the east side of Sylvester Gulch reportedly encountered relatively high ground <br />water inflow as Sylvester Gulch was approached in 1954. There is no evidence of flow out of the <br />audit at the present time. This is consistent with Mountain Coal Company's experience in the F - <br />Seam as Sylvester Gulch was approached and overburden thinned. <br />Somerset Mine (formerly U.S. Steel) mining operations north of the North Fork encountered higher <br />inflows when mining approached a level at or below the level of the North Fork. It is expected that <br />similar conditions will exist within a small area of Mountain Coal Company's property below the <br />level of the North Fork. <br />The surface effects of mining on the hydrologic balance in the SOD area are anticipated to be <br />minimal. Section 2.05.6 (6) in this document describes at length the anticipated impacts to the <br />ground surface resulting from mining activities in the SOD. It is acknowledged throughout this <br />permit that numerous landslides and slumps are present throughout the MCC permit area and <br />these features generally move in respons& to saturation by precipitation events. Monitoring plans <br />included in 2.05.6 (6) describe how MCC will observe these features for effects due to mining <br />related activities. <br />If, through the monitoring activities, it is determined that mine -related subsidence causes new <br />movement of landslides and slumps MCC will mitigate damages to the impacted drainages. For <br />example, if stream courses are blocked by mining induced slide movement, MCC will use hand <br />tools or appropriate heavy equipment to reopen affected channels. The necessary permits to <br />perform such work will be obtained prior to performing mitigation. Other mitigation could <br />include the placement of straw bale dikes or silt fences below slide areas to reduce sediment <br />loading. Stream channels and ditches will be repaired using bentonite, bentonite/soil mixes, or <br />available soil to fill cracks if they occur in the channel bottoms and divert water. Culverts could <br />also be used to temporarily maintain stream flows until other appropriate mitigation can be <br />implemented. If ponding occurs within the stream channels and is not determined to create a <br />hazard to the public, no additional mitigation is proposed. However, if the ponding creates <br />hazardous conditions, the structure creating the ponding may be breached or bypass channel <br />built. The mitigation work will only be accomplished after the appropriate permits are obtained. <br />If subsidence of existing SOD wetlands raises the water table to a point where the wetlands are <br />in danger of destruction, the CDMG and Forest will be notified and appropriate actions be taken. <br />These actions may include excavating the portion of the channel that has created the damming <br />effect on the wetlands. No action may be appropriate where the ponding would result in an <br />overall increase in wetlands and creation of habitat that would benefit waterfowl and other <br />wildlife. <br />If subsidence in the area of SOD wetlands creates a change in the Gradient that would result in a <br />lowering of wetland water table, modifications to the stream channel to stabilize the water table <br />may be necessary. The mitigation efforts may include the construction of rock darns or weirs <br />that would act as impediments to stream flow and result in the re-establislunent of the wetland <br />water table levels. The Best Currently Available Teclulology will be used to restore the water <br />• levels of the wetlands if necessary and only implemented after obtaining approval. <br />2.O5-184 Revised June 200.1 PRIO, January 2006, Harc% 2006: Rev. A1ay 2006 PRIO, Nov. 2006 TRI07; Sep. 2007 PR12, Feb 2008 PR12 <br />