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STOCK POND T -3 <br />PERMANENT POND DEMONSTRATION <br />In 1991, SCC has constructed a stock pond south of the shop area and on the fill side of the haul road <br />at the II -W Mine and, along with the land owner, believes that the pond should remain permanent. The <br />location of this stock pond T -3 is shown on Exhibit 20 -2, Postmining Topography Map. The purpose <br />of this evaluation is to demonstrate that Stock Pond T -3 meets the design criteria specified in Rule <br />4.05.9 for permanent impoundments. <br />Water Quality <br />This stock pond is located along side a permanent haul road and contains water that originates from <br />surface runoff from the haul road. There is no indication that the runoff contains potentially acid or <br />toxic forming material that could adversely impact surface water quality. Results of the 2012 water <br />sample analysis are attached. The analysis indicates that the water is suitable for the approved post <br />mine land use that includes livestock grazing and wildlife habitat. <br />Water Persistence <br />It is expected that this stock pond will hold water from the spring runoff through early summer at a <br />minimum. <br />Accessibility <br />This pond is easily accessible to livestock and wildlife. There are no drop offs or excessively steep <br />slopes around the edges of this pond. <br />Cgpacily <br />The water storage capacity for T -3 is 0.02 ac. ft. Since the capacity is under the 2 ac. ft. limit, the <br />State Engineer's office does not need to review the permanency request and the pond should not have <br />any significant effect on downstream users. A general stability analysis was conducted for stock ponds <br />based on the construction methods and material characteristics. A predicted Factor of Safety of 1.56 <br />was calculated by this analysis. This stability analysis is contained in Attachment 13 -11 and a <br />summary copy is attached. <br />Pond Dimensions <br />The dimensions and capacity for this stock pond are shown in the PAP on Exhibit 13- 27.T3, Stock <br />Pond T -3 Survey. As shown on the as-built drawing, the embankment is 5 feet in height as measured <br />from the pond bottom to the invert of the spillway; however the pond was excavated to provide fill for <br />the embankment. Therefore the embankment is less than 5 feet in height from the upstream natural toe <br />of the embankment to the invert of the spillway. The combined slope of all the embankments do not <br />exceed 5V:1H with no slopes greater than 2H:1V. <br />