2009-11-03_PERMIT FILE - C1994082

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STOCKPOND 011A PERMANENT POND DEMONSTRATION • SCC has constructed a stock pond in the north reclaimed area at the Yoast Mine and, along with the land owner, believes that the pond should remain permanent. The location of this stock pond 011A is shown on Exhibit 20-2, Postmining Topography Map. The purpose of this evaluation is to demonstrate that Stock Pond 011A meets the design criteria specified in Rule 4.05.9 for permanent impoundments. Water Ouah This stock pond is located in the upper reaches of the watershed and contains water that originates from surface runoff from the Yoast reclamation area. There is no indication that neither the spoil nor the replaced topsoil contains potentially acid or toxic forming material that could adversely impact surface water quality. Results of the 2009 water sample analysis are attached. The analysis indicates that the water is suitable for the approved post mine land use that includes livestock grazing and wildlife habitat. Water Persistence It is expected that this stock pond will hold water from the spring runoff through early summer at a minimum. ty Accessibili This pond is easily accessible to livestock and wildlife. There are no drop offs or excessively steep slopes around the edges of this pond. Ca aci • The water storage capacity for Pond 011A is 1.7 ac. ft. Since the capacity is under the 2 ac. ft. limit, the State Engineer's office does not need to review the permanency request and the pond should not have any significant effect on down stream users. A general stability analysis based on the construction methods and material characteristics is included in Attachment 13-19, As-Built Report Sediment Structure Pond 011A. A Factor of Safety greater than 1.8 was calculated by this analysis. Pond Dimensions The dimensions and capacity for this stock pond are shown in the PAP on Exhibit 13-5C, Pond 011A As-Built. As shown on the as-built drawi{}g, t o e}I}b4#7kx. ent daps not exceed 5 feet in height as measured from the upstream toe of the embankment to the invert of the spillway. The combined slope of all the embankments do exceed 5V:1H but with no slopes greater than 2H:1V. Postmine Land Use The approved land use for the Yoast reclamation area is livestock grazing and wildlife habitat. This stock pond will enhance the postmine land use in this area. Snillwav Cauaci The peak discharge, spillway capacity and armoring requirements were determined using SEDCAD4 (see Attachment 13-19, As-Built Report Sediment Structure Pond 011A). The peak discharge was determined using the methodology outlined in this permit. The spillway capacity was determined using SEDCAD4 and was constructed with a 10 foot bottom width and a minimum depth of 1.6 feet. • NM-29 1 Revised 8/09