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Susan Burgmaier -8- February 7, 2014 <br />a new Structure Summary, and Subwatershed Detail is provided. Please see revised <br />pages App. B -35 to 39 ( Subwatershed Hydrology Detail). Please also see revised <br />page App. B -15 (Structure Summary). Page numbering, beginning on page App. B -15 <br />through the end of Appendix B have been revised due to numerous changes in page <br />numbering. Please see revised pages App. B -15 to B -83. <br />30. DRMS: Pages App. B -66 - 68 indicate that the 100 -yr runoff from Drainage Area D is <br />11.64 cfs, and the 10 -yr event is 3.47 cfs. BRL has provided a Sedcad run for the <br />Drainage Area D 10 —yr event (beginning on page App. 8 -25), but we do not see any <br />documentation for the 100 -yr event. Please provide calculations or Sedcad run <br />for the 100 -yr event on Drainage Area D. (Rules 2.05.3(4)(a)(ii) and 4.10.3) <br />B W2: Please the 100 -year event for drainage area "D" beginning on page Exh 8 -25iv. <br />31. DRMS: The proposed revision materials indicate that Watershed H will be enlarged, <br />as shown on Map 20, and new designs for Ditches H1 and H2 are provided. There does <br />not appear to be a revised design for Culvert H1 in the submittal. Please provide a <br />revised design for Culvert H.I. to reflect the proposed increased acreage of <br />Watershed H, (Rule 2.05.3(4)(a)(ii)) <br />BOW2: Please see revised page Exh. 8 -168. The SedCad design shows a minimum of <br />30" culvert to be installed. A 42" culvert is installed. <br />32. DRM Buckhorn's analysis determines that the pile configuration proposed under <br />TR -84 will provide a long -term static Factor of Safety (FoS) of 1.5, in accordance with <br />Rule 4.09.1. The report text does not specifically address Rule 4.10.4(2), which <br />requires coal mine waste banks to have a minimum static FoS of 1.5 (not limited to the <br />"long- term" condition). Previous studies prepared by Buckhorn for the Bowie No. 2 <br />Mine (for TR -44, TR -45, TR -56, TR -64, etc.) have considered the effects of pore <br />pressure, and evaluated total stress, not only effective stress when determining the <br />critical FoS. The TR -45 Buckhorn analysis dated 29- Mar -2007 evaluated a number of <br />pile geometries, as tabulated on Page 14 of that report. For "Cross Section A ", the 2nd <br />and 4th entries give Total Stress Analysis FoS of 1.46 and 1.44, respectively, for block <br />failure. (The 2nd entry, 2.5h:1V, with a pile height of 100', is very similar to what is <br />now being proposed.) Please address the requirements of4.10,4(2) (minimum <br />static FoS of 1,5) for this proposed reconfiguration of Gob Pile #3, Based on <br />pre vious stability analyses performed, this will include a consideration of the <br />dissipation of pore pressures, if any, as the coal mine waste is dewatered, <br />over time, <br />B W2: Please see Buckhorn's response which is attached. <br />33. DRM : Section 6.0 of the TR -45 (29- Mar -2007) Buckhorn report provides a list of <br />