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STOCK POND T -18 <br />PERMANENT POND DEMONSTRATION <br />In 1998, SCC constructed a stock pond in the north reclaimed area at the 11 -W Mine and, along with <br />the land owner, believes that the pond should remain permanent. The location of this stock pond T -18 <br />is shown on Exhibit 20 -2, Postmining Topography Map. The purpose of this evaluation is to <br />demonstrate that Stock Pond T -18 meets the design criteria specified in Rule 4.05.9 for permanent <br />impoundments. <br />Water Quality <br />This stock pond is located in the upper reaches of the watershed and contains water that originates <br />from surface runoff from the H -W reclamation area. There is no indication that neither the spoil nor <br />the replaced topsoil contains potentially acid or toxic forming material that could adversely impact <br />surface water quality. Results of the water sample analyses are attached. The analysis indicates that <br />the water is suitable for the approved post mine land use that includes livestock grazing and wildlife <br />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 />Ca aci <br />The water storage capacity for T -18 is 1.88 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. This stability analysis is contained in <br />Attachment 13 -11. A predicted Factor of Safety of 1.56 was calculated by this analysis. <br />Pond Dimensions <br />The dimensions and capacity for this stock pond are shown in the PAP on EY>hihit 13 -27. i 18, Stoc <br />Pond T -18 Survey. As shown on the as-built drawing, the embankment is 5.5 feet in height as <br />:_:: �, t,�•� :: �:_: w =_.z ��� botto..., to- the iinvere of the spillway; however the pond was excavated to <br />provide fill for the embankment. Therefore the embankment is less than 5 feet in height from the <br />upstream natural toe of the emba- Amie..t to the anvc—r! of t.-.: ___ ll <br />embankments do not exceed 5V: 1 H with no slopes greater than 2H:1 V. <br />MR -76 T -18.1 Revised 12113 <br />