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Mr. Jim Stover, P.E. <br />July 16, 2008 Page 3 <br />amended Map Figure 2.2-2, however Light Use Road #3 is (apparently <br />erroneously) not depicted or labeled on the map figure. <br />Please provide amended map Figure 2.2-2, with Light Use Road #3 depicted <br />and labeled. <br />Rule 2.05.3(4) Ponds, Impoundments, Other Treatment Facilities and Diversions <br />14. Item Resolved. <br />15. Item Resolved. <br />16. The Division concurs that the new sediment pond embankment is not a Class B or <br />C dam and failure will not cause serious property damage or loss of life. <br />However, a stability analysis is required for all impoundment embankments. In <br />accordance with 4.05.9(8)(b), any impoundment not meeting the size or other <br />criteria of 30 CFR 77.216(a), and located where failure would not be expected to <br />cause loss of life or serious property damage, shall have a minimum static safety <br />factor of 1.3 for a normal pool with steady state seepage saturation conditions. <br />Please provide a stability analysis for the proposed new impoundment that <br />demonstrates compliance with 4.05.9(8) (b). <br />17. Item Resolved. <br />18. Item resolved. <br />19. It is still unclear how the new sediment pond will be operated (manually versus <br />passively discharged). The revised SEDCAD demonstration shows that the pond <br />will discharge through the primary spillway during the 10-year, 24-hour <br />precipitation event. Yet the operator has indicated in their response to Item 20 <br />below that the pond is designed to contain the 10-year event. <br />The Elevation-Capacity-Discharge Table provided for the 10-year event does not <br />show the top of sediment storage elevation. There is also no Structure Summary <br />provided showing the peak settleable solid concentration out of the pond, which is <br />required for the 10-year event demonstration to show compliance with 4.05.2(7). <br />On revised Figure 2.2-3, the sediment storage level is given on Section AW at <br />5415.5 feet, which is equivalent to the primary spillway elevation. This appears <br />to indicate that no treatment would be provided and there is no room for sediment <br />storage (if the pond is passively discharged as indicated by the SEDCAD <br />demonstration). <br />If the pond is manually discharged, the outflow would have to be sampled every <br />time to show compliance with water quality standards and effluent limitations.