2020-07-13_REVISION - C1981008 (2)

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2. The untreated drainage from the disturbed area ceases to contribute additional suspended solids above natural conditions, and 3. The drainage leaving the pond meets applicable State and Federal water quality requirements, if any, for the receiving streams. The ponds will be removed when the appropriate sections of the regulations are satisfied. When the ponds are removed, the affected land will be regraded and revegetated pursuant to the DRMS's regulations, Section 4.05.17 and the approved New Horizon Reclamation Plan. Dam Classification Criteria The dam classification criteria follow the guidelines of the USDA Soil Conservation Service Technical Release 60 regarding potential for loss of life and damage as a result of dam failure. This classification criterion is shown below. • Class A: No realistic threat of damage to property or life in case of dam failure. • Class B: Dams located in predominately rural or agricultural areas where failure may damage isolated homes, main highways or minor railroads or cause interruption of use or service of relatively important public utilities. • Class C: Dams located where failure may cause loss of life,serious damage to homes,industrial and commercial buildings, important public utilities, main highways, or railroads. Special demonstrations are needed for ponds that have Class B or C dams. It is demonstrated below that each of the ponds meets the Class A criteria. Ponds 012 and 013 - As seen on Map 2.05.3(3)-1 Surface Hydrology, Ponds 012 and 013 are located immediately outside the floodplain of Tuttle Draw. Any dam break of these ponds would discharge water directly into Tuttle Draw. There is no chance the water could harm anything or anyone at other locations. There are no structures that could be affected by a small volume in Tuttle Draw since it is large enough to handle substantial peak flows, as shown on Map 2.05.3(3)-l. For these reasons, Ponds 012 and 013 are given a Class A designation. Ponds 015, 016, and 018 - Since these ponds are designed to contain the flow from a 100-year, 24- hour event they would only contribute a couple acre-feet to a drainage from overflow or embankment failure. Thus, these ponds are given a Class A designation. Stock Ponds -Prior to mining, a small stock pond existed on the Goforth property (see Map 2.04.9- 1); therefore, a replacement stock pond(SP 1)was constructed in the postmining surface. Another stock pond(SP2)will be constructed on ERMR property by backfilling and regrading a portion of Pond 009. Applicable technical information has been included in Attachment 2.05.3(3)-38 and - Section 2.05.3(3) Page 12 July 2020 (TR-99)