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Doug White, Western Fuels Dec. 17, 2012 <br />C -2010 -089 / MR -02 & TR -01 PAR. Page 3 of 4 <br />7. The sedimentology portion of the SEDCAD run provided for pond NHN -001 utilizes a <br />control practice factor (C) of 0.45. The curve number used for the watershed (91) <br />indicates that the area is bare. Therefore, the "C" value should be 0.9. Please revise the <br />design accordingly. <br />Engineering/ Geotechnical <br />The approved design for Pond NHN -001, prepared by Arcadis U.S., Inc., is provided in <br />Appendix 2.05.3(4) -1 of the permit. DBMS requirements for pond embankment construction are <br />prescribed in Section 4.05.9 of the Coal Regulations. A list of the applicable sections, with <br />comments, is provided below. [The NHN -001 embankment height is less than 10 feet from the <br />bottom of the channel to the bottom of the spillway, and this pond does not meet the USDA SC,S <br />TR60 criteria for a Class B or C impoundment, therefore, many of the requirements of 4.05.9 are <br />not applicable.] <br />4.05.9(2) - A combination of principal (culvert pipe with gated weepholes) and emergency (open <br />channel) spillway systems was provided, as were barriers to control piping along the <br />primary spillway conduit. Item satisfactorily addressed. <br />4.05.9(7) - Requirements for all impoundment embankments <br />(a) Was vegetative /organic material removed from foundation area? Was the <br />foundation base scarified? <br />1. Please provide a statement addressing these requirements. <br />(b) Was the fill material free of sod, roots, vegetative matter, and frozen soil? <br />2. Please provide a statement addressing this requirement. <br />(c) What layer thickness was used in constructing the embankment? Was 90% <br />compaction deemed sufficient for stability? (The Arcadis design may not have <br />addressed these issues.) <br />3. Pleaseprovide statements addressing these requirements. <br />(d) Is the top elevation i' higher than the water elevation in the emergency spillway <br />will be, during an event? Will this be the case once any settlement has occurred? <br />4. Please provide a statement addressing this requirement. <br />(e) Are the combined upstream and downstream slopes not steeper than 5H: l V (they <br />are 6H:1 V), is neither steeper than 2H: l V (each is 3H:1 V). Item satisfactorily <br />addressed. <br />4.05.9(8) - Stability <br />(b) A minimum static safety factor of 1.3 for a normal pool with steady state seepage <br />saturation conditions is required. Lambert's study evaluated the sudden <br />drawdown condition, but did not determine a factor of safety for the required <br />