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West Elk Mine <br />• There is a very small risk (WWE has calculated the risk to be less than one percent) that one or <br />more of the stock ponds in the pemut area could be adversely affected via surface cracks. Pond <br />water could be diverted into locally permeable zones within the overburden where it could: (1) <br />Migrate down-dip towazd the North Fork or Dry Fork to become pazt of the tributary <br />alluvial/colluvial contribution of baseflow to the stream system, (2) Reappear as an ephemeral <br />seep or spring, or (3) Become trapped as storage in an isolated zone within the overburden. If <br />any of these circumstances were to occur, they would render the affected stock pond temporarily <br />useless for retaining surface water. However, the lost water would eventually return to the Dry <br />Fork and/or North Fork. The stock pond embankments could conceivably be affected by <br />surface cracking; although, the probability of this occurring is insignificant. <br />It is important to note that the overburden materials in the permit azea contain numerous shale and <br />claystones layers and lenses which tend to undergo plastic deformation under compression, thereby <br />sealing fractures that develop. In addition, the sediment load within surface flows (especially during <br />spring runoff) will tend to fill surface cracks which may develop, thus further reducing the potential <br />to transmit water downward. <br />The most severe potential subsurface hydrologic consequences include: <br />• Formation of interconnected fractures in the fracture zone with local water-bearing units of the <br />overburden, thereby inducing either: (1) The movement of groundwater from one formation to <br />another or (2) Loss of water to the mine workings. Should diversion to the mine occur, this <br />water will be collected, treated, and dischazged into the North Fork or the Dry Fork (see <br />• discussion above regazding the implications of surface water discharges to the North Fork and <br />Dry Fork). <br />As discussed extensively within this permit document, there are no regional aquifers within the <br />Mesaverde Formation in the vicinity of West Ells Mine, nor is there demonstrated formation <br />groundwater use at the mine or in the general azea. Consequently, there aze no aquifers which <br />could be damaged as a result of subsidence. While there has been a sizeable amount of <br />groundwater inflow observed from recently encountered fault systems (BEM and 14HG) there <br />is no evidence to indicate any use of that water regionally. In addition, the observed inflows <br />from these fault systems have decreased over time to a small percentage of the initial inflows, <br />similar to other groundwater encounters in the mine. <br />Interconnection of fractures filled with water and methane (as reported in the Oliver No. 2 <br />Mine) with the mine workings via the B or E Seam fracture zone. This subject is discussed <br />later in this section and in Exhibit 60. <br />As discussed in Section 2.05.6(6)(e)(i) Potential Impacts from Local Seismic Activity, subsidence <br />could accelerate the naturally-occurring rockfall and landslide propensities that are already evident <br />in the permit area, but this will not constitute a hazard to either people or property nor would this <br />measurably impact the surface or ground water hydrology of the azea. <br />Cracking of the earth along or across the trails or unimproved roads of the coal lease azea already <br />naturally occurs, but in the "worse case" could be accelerated by, or additional cracks created by, <br />subsidence. As the trails and roads are unimproved, typically only all-terrain or four-wheel drive <br />vehicles aze utilized and rough terrain is expected, so the hazazds created by any additional <br />1.05-118 Revised June 1005 PRIG, Rev. March 1006; May 1006 PRIO <br />