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West Elk Mine Reservoirs and Stock Ponds Map 37 shows the locations of all reservoirs and stock ponds within the current permit and lease areas. A total of 36 stock ponds aze located iri or near the current permit area, and 1 pond is located in the Box Canyon permit revision area. No effects of mining to these ponds have been observed during F-Seam retreat mining or from B-Seam longwall mining. Within the permit azea, the majority of the stock ponds are owned by the U.S. Forest Service (none of which aze known to be decreed rights). The stock ponds aze used on a seasonal basis. These ponds derive their water from surface flows and they are typically constructed via a low, earthen dam across a defined drainage. The total storage volume of the stock ponds in the permit area is estimated to be 17.5 acre-feet based on an average storage capacity of 0.5 acre-feet. The probable hydrologic consequences of the longwall mining for stock ponds in the permit azea aze much the same as they are for streams in the permit azea. These ponds aze supplied by surface runoff or spring flow. Disruption of the water supply to these ponds by mining is not likely because the minimum overburden thickness between the B-Seam and the lowest elevation pond is 900 feet and between the E-Seam and the lowest elevation pond is 700 feet. Given that the combined height of the caved/fractured zone is 270 feet above the B-Seam or 250 feet above the E-Seam, it is cleaz that none of the stock ponds will be affected by subsurface cracking. Additional discussions and data on stock ponds can be found in the Annual Hydrology Reports, 1986 to present. There is, however, the potential for surface cracking to either directly or indirectly affect the ponds, • via one (or both) of the following mechanisms: 1. Streamflows in the azea tributary to a stock pond are intercepted by a surface crack and prevented (or reduced) from reaching the pond. 2. A surface crack forms directly beneath the pond or the embankment, thereby causing water loss or dam failure. As discussed extensively in Section 2.05.6 (3)(b)(iii & viii) Surface Water Quantity Effects, the probability of encountering cracks in the Apache Rocks and Box Canyon permit revision area is extremely low based upon data obtained after mining the 1NW through 8NW longwall panels. When cracks aze encountered, they aze likely to be over the chain and barrier pillars. Cracks that form in the internal portion of panels will tend to heal themselves quickly (see earlier discussion). Superposition of the stock ponds on the B and E-Seam mine plans indicate that only two of the Apache Rocks permit revision azea ponds and one Box Canyon permit revision area pond are located on or in close proximity to the chain and bamer pillazs. Although the risk of surface cracking to stock ponds is small, there aze mitigating factors that should also be considered. First, because the ponds are located in drainages, cracks will tend to seal themselves through the deposition of sediments conveyed by snowmelt and rainfall-runoff. Second, it will be feasible to monitor the response of the stock ponds to mining and to take mitigating steps (i.e., fill in the crack), if necessary. • 2.05-/67 November 100 PRlI