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• INTRODUCTION Seneca Coal Company (SCC) constructs temporary stock tanks in the reclaim areas at the Seneca operations. These small tanks will benefit both livestock grazing and wildlife utilization and will enhance the interim and final postmining land use of the reclaimed areas. The stock tanks slow the peak runoff from precipitation events and snowmelt and help to minimize erosion in the reclaimed area. DESIGN The stock tanks are small structures to enhance the postmine livestock and wildlife utilization. The capacity of the tanks are less than two acre-feet and the vertical height of the embankments is five feet or less, as measured from the from the upstream toe to the bottom of the emergency spillway. The drainage area for each tank is large enough to maintain an adequate supply of water into the tank. All stock tank locations are in drainages that are normally dry. CONSTRUCTION All permanent and temporary stock tanks will meet the design criteria specified in the Regulations of the Colorado Mined Land Reclamation Board (Rule 4.05.9). All impoundments intended to be retained as permanent postmining features shall comply with applicable state engineer rules and regulations. Access to the tank • sites, in reclaimed areas, during the construction phase will be along drainage bottoms or along temporary access roads to minimize damage to vegetation. If necessary, access routes will be reseeded with an approved seed mix. All topsoil will be salvaged prior to tank construction and spoil material will be used for construction of the embankments. After construction, topsoil will be replaced on the embankment and adjacent disturbed areas above the elevation of the emergency spillway. Each site will be seeded with the approved seed mix. POND STABILITY A generic stability analysis was completed to assess the stability of the embankments forming the stock ponds. Instead of completing an analysis for each potential pond, a worst case scenario has been evaluated. If the worst case scenario proved to be stable, then the other embankments with lesser height and shallower slopes should be stable. Stability Analysis A force limit equilibrium stability analysis was completed using the SLOPE/W software package. A Morgenstern Price analysis was used in conjunction with a search routine to estimate the lowest safety factor for the embankment. This method satisfies both moment and force equilibrium of a given analysis. • For the worst case scenario, embankment geometry with the following characteristics was used: