Laserfiche WebLink
Wesr Elk Mrne <br />• Reservoirs and Stock Ponds <br />Map 37 shows the locations of all reservoirs and stock ponds within the current pemut and lease <br />azeas. A total of 36 stock ponds aze located in or near the current pernut azea, and 1 pond is located <br />in the Box Canyon permit revision azea. After SOD is approved, approximately 51 ponds will be <br />located in the permit azea. No effects of mining to these ponds have been observed during F Seam <br />retreat mining or from B Seam longwall mining. Within the pemut area, the majority of the stock <br />ponds are owned by the U.S. Forest Service (none of which aze known to be decreed rights). The <br />stock ponds are used on a seasonal basis. These ponds derive their water from surface flows and <br />they aze typically constructed via a low, earthen dam across a defined drainage. There are an <br />additional 14 stock ponds in the South of Divide permit area. The total storage volume of the <br />stock ponds in the South of Divide permit area is estimated to be 7 acre-feet based on an <br />average storage capacity of 0.5 acre-feet. (See section 2.2 of Exhibit 71 for more information.) <br />The probable hydrologic consequences of the longwall mining for stock ponds in the pemut area are <br />much the same as they are for streams in the permit azea. These ponds are supplied by surface <br />runoff or spring flow. Disruption of the water supply to these ponds by mining is not likely because <br />the minimum overburden thickness between the E Seam and the lowest elevation pond is 500 <br />feet. Given that the combined height of the caved fractured zone is 280 feet above the E Seam, <br />it is cleaz that none of the stock ponds will be affected by subsurface cracking. Additional <br />discussions and data on stock ponds can be found in the Annual Hydrology Reports, 1986 to <br />present. <br />• There is, however, the potential for surface cracking to either directly or indirectly affect the ponds, <br />via one (or both) of the following mechanisms: <br />1. Streamflows in the azea tributary to a stock pond aze intercepted by a surface crack and <br />prevented (or reduced) from reaching the pond. <br />2. A surface crack forms duectly beneath the pond or the embanlanent, thereby causing water loss <br />or dam failure. <br />As discussed extensively in Section 2.05.6 (3)(b)(iii & viii) Surface Water Quantity Effects, the <br />probability of encountering cracks in the South of Divide pemrit revision area is extremely low <br />based upon data obtained after mining the 1NW through 8NW longwall panels. When cracks are <br />encountered, they are likely to be over the chain and bamer pillazs. Cracks that form in the internal <br />portion of panels will tend to heal themselves quickly (see eazlier discussion). Superposition of the <br />stock ponds on the E Seam mine plans indicate that roughly half of the ponds are located on or <br />in close proximity to the chain and barrier pillars. <br />Although the risk of surface cracking to stock ponds is small, there are mitigating factors that should <br />also be considered. First, because the ponds aze located in drainages, cracks will tend to seal <br />themselves through the deposition of sediments conveyed by snowmelt and rainfall-runoff. Second, <br />it will be feasible to monitor the response of the stock ponds to mining and to take mitigating steps <br />(i.e., fill in the crack), if necessary. <br />2.05-206 Revised June 1005 PRIO; Rev. March 2006; Rev. Apri11006 PRIO; May 1006 PR/0 <br />