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SEDIMENT POND 010 <br />• PERMANENT IMPOUNDMENT DEMONSTRATION <br />In conjunction with Technical Revision 37, SCC applied for approval of Sediment Pond 010 as a permanent <br />impoundment to support the post mining land use of livestock grazing and wildlife habitat. Under applicable <br />provisions of Rule 4.05.9(13), Sediment Pond 010 must meet the following criteria: <br />(a) The quality of the impounded water shall be suitable on a permanent basis for its intended use, shall meet <br />applicable state and federal water quality standards and discharge of water from the impoundment shall <br />meet applicable State and Federal effluent limitations and shall not degrade the quality of receiving water <br />below applicable stream standards; <br />(b} The level of water shall be sufficiently stable, and the configuration of the pond shall be adequate, to <br />support the intended use; <br />(c) Adequate safety and access to impounded water shall be provided for proposed water users; <br />(d) Water impoundments shall not result in the diminution of the quality or quantity of water available to water <br />right holders for agricultural, industrial, recreational, or domestic uses except in accordance with applicable <br />state law; <br />(e) The size of the impoundment shall be adequate for its intended purposes; <br />(f) The impoundment shall be suitable for the approved post-mining land use. <br />Detailed discussions and relevant information is presented in the PAP in various sections of Tab 7, Hydrology and <br />Tab 13, Facilities. The following is a summary of the details contained in the PAP. <br />Rule 4.05.9(13)(a). Pond 010 is located in the perennial Annand Draw, which is tributary to Grassy Creek. The <br />location of this pond is shown on Exhibit 20-2, Postmining Topography Map. CDPHE has determined that <br />beneficial uses in Annand Draw include aquatic life and agricultural uses. In 2007/2008, water quality parameters <br />from Pond 010 discharges were below CDPHE agricultural standards, indicating that these waters are suitable for <br />irrigation and livestock use. Attached is a tabulation of the recorded "Excursions of CDPHE Stream Standards" for <br />the 12 month period (7/01/07 to 6/30/08). <br />Rule 4.05.9(13)(b). This pond was constructed in August of 1996. Flow was observed for the first time ever on <br />February 24, 1997. The pond receives perennial inflow from seeps and springs, as well as snowmelt runoff during <br />spring months. Flows have ranged from 0 to 543 gpm with a mean of 71 gpm. <br />The pond is fitted with a prindpal spillway that controls the permanent pool elevation. Total freeboard (invert of <br />orifice to top of embankment) = 10.0 feet. Freeboard (invert of orifice to invert of emergenry spillway) = 3.6 feet. <br />Freeboard (invert emergency spillway to top of embankment) = 6.4 feet. In 2007 water capacity was surveyed and <br />calculated, the water storage capacity was measured at 5.3 ac ft (top of sediment to invert of orifice). Additional <br />detailr and dircucrionr are contained in the PAP in Tab 13, Attachment 13-3A, As-Built Report Sediment Structure Pond 010 and <br />on Exhibit 13~A, A.r-Built Pond 010. <br />Pond 010 is generally D shaped. This configuration is typical of stock water impoundments throughout northwest <br />Colorado. Pond 010, as currently configured, is adequate to support its intended future use as a Livestock Watering <br />Tank. <br />Rule 4.05.9(13)(c). The pond has relatively shallow inslopes (3H:1 V or shallower). There are no cliffs or steep <br />• dropoffs along any pond margin. <br />TR-37 1 08/08 <br />