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<br />• documentation previously provided in Appendix C to the WESTEC Report has been <br />superseded and revised design informatton is presented in Appendix B, Protection of the <br />Hydrologic Balance. Please see accompanying revisions. <br />47. OCM proposes to add another 24"culvert at the Second Drainage, where diverted water from <br />above the fill is carried. Please provide design information for the culvert, and include its <br />location on Maps E-3111 and E-3214. <br />Responses: Please refer to previous Responses 31, 32, 33, and 46. With relocation of the <br />upland diversion, a culvert is no longer required and has been eliminated. Please see <br />accompanying revisions. <br />48. The worksheets in Appendix C for two culverts, Existing RR Culvert and Additional Second <br />Drainage West Culvert, are for circular channels. DMC is not familiar with calculations for <br />circular channels or with the Ffowmaster program. We attempted to verify the proposed culvert <br />sizing with the culvert sizing utility in SEDCAD+'M, and using the culvert Homographs in the <br />Handbook of Steel Drainage and Highway Construction Products, and found that both methods <br />resulted in the requirement for considerably larger diameter culverts tan those proposed. Inputs <br />were identical to those used in OCM's worksheet, with the exception ojassumptions we made for <br />two unknowns, headwater and culvert length. Even varying the two unknowns, our results <br />were consistently larger diameters. Please provide additional information and supporting details <br />for OCM's calculations. <br />• Responses: Please refer to previous Responses 37 and 46. Because the existing railroad <br />culvert ~s not part of the proposed Project and with relocation of the upland diversson, <br />drainage design calculations for both of these culverts have been eliminated. Standard <br />culvert design and sizing methods have been utilized for all culvert designs and revisions as <br />presented in the revised design package provided for insertion in Appendix B. <br />49. OCM has designed ponds which will contain the 10-year, 24-hour precipitation event, and will <br />be manually dewatered An indicator should be installed in all ponds which shows the <br />maximum water level which can be accumulated while still allowing ample capacity for the 10- <br />yearevent. <br />Responses: A post or pipe with a painted water level mark will be installed in the ponds as <br />a reference for operational dewatering. It should be noted that Oxbow has successfully <br />utilized manual dewatering as a means of controlling both pond storage levels and storm <br />water storage capacity and suspended solids. The capability of increasing detention times <br />through manual dewatering has allowed Oxbow to significantly decrease suspended solids <br />levels in the pond discharge. Effective pond management has also prevented the existing <br />ponds from overtopping at any time to date. <br />2.05.3(7) Coal Handling Structures <br />S0. Under 9aJ it states that the existing conveyor from Sanborn Creek mine is to be changed to 42- <br />inches. It is our understanding that this conveyor will be changed to 48-inches with the new <br />expansion. If this is the case please give the correct information. <br />Responses: Please refer to previous Response 20 above. <br />