2017-04-05_PERMIT FILE - C1982057 (10)

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SEDIMENT POND 005 PERMANENT IMPOUNDMENT DEMONSTRATION SCC has applied for approval of Sediment Pond 005 as a permanent impoundment to support the post mining land use of livestock grazing and wildlife habitat. This application comes at the request of the landowner (Salt River Project) to retain the pond. Under applicable provisions of Rule 4.05.9(13), Sediment Pond 005 must meet the following criteria: (a) The quality of the impounded water shall be suitable on a permanent basis for its intended use, shall meet applicable state and federal water quality standards and discharge of water from the impoundment shall meet applicable State and Federal effluent limitations and shall not degrade the quality of receiving water below applicable stream standards; (b) The level of water shall be sufficiently stable, and the configuration of the pond shall be adequate, to support the intended use; (c) Adequate safety and access to impounded water shall be provided for proposed water users; (d) Water impoundments shall not result in the diminution of the quality or quantity of water available to water right holders for agricultural, industrial, recreational, or domestic uses except in accordance with applicable state law; (e) The size of the impoundment shall be adequate for its intended purposes; (f) The impoundment shall be suitable for the approved post- mining land use. Detailed discussions and relevant information is presented in the PAP in various sections of Tab 7, Hydrology and Tab 13, Facilities. The following is a summary of the details contained in the PAP. Rule 4.05.9(13)(a). Pond 005 is located in an un -named drainage along the original North Entrance Road to the II -W Mine, a tributary to Dry Creek. The location of this pond is shown on Exhibit 20 -2, Postmining Topography Map. CDPHE has determined that beneficial uses in Dry Creek include aquatic life and agricultural uses. In 2011 water quality parameters from Pond 005 discharges were below CDPHE agricultural standards, indicating that these waters are suitable for irrigation and livestock use. Attachment A contains a tabulation of the water quality analyses that list "2011 Excursions of CDPHE Stream Standards" for the 12 month period (1/01/11 to 12/3 1/ 11) Rule 4.05.9(13)(b). This pond was constructed in 1992. The pond receives perennial inflow from seeps and springs, as well as snowmelt runoff during spring months. The pond is fitted with a principal spillway that controls the permanent pool elevation. Total freeboard (invert of principal spillway to top of embankment) = 7.4 feet. Freeboard (invert of principal spillway to invert of emergency spillway) = 1.9 feet. Freeboard (invert emergency spillway to top of embankment) = 5.5 feet. In 2011 water capacity was surveyed and calculated, the water storage capacity was measured at 4.3 ac ft (top of sediment to invert of principal spillway). Additional details are contained in the PAP in Tab 13, on Exhibit 13 -5A, As -Built Pond 005. MR -76 1 09/13