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Response to DRMS Adequacy Review(2)—Cotter-9 Mine Reclamation Plan Amendment <br /> Cotter Corporation (N.S.L.) ("Cotter") submits this response to the November 26, 2013 letter <br /> from Travis Marshall, Division of Reclamation, Mining and Safety ("DRMS"), to Glen <br /> Williams, Cotter. The DRMS' comments are in italics and Cotter's responses are in bold. <br /> 1. Page ESWMP-1 response-settling ponds on Monogram Mesa... <br /> a. The August 1, 2013 clarification response is adequate. <br /> b. How is water managed in the lowermost pond? The response that "ponds will be <br /> designed at a later date" is inadequate. As these ponds are part of the required <br /> EPP, designs are required prior to approval of the EPP. <br /> The ponds will be designed at a later date to provide adequate capacity for the <br /> mine water as well as the precipitation. This design will be forwarded as a <br /> Technical Revision prior to resuming mining activity at the site. <br /> c. Is "several inches of freeboard" in the lowermost pond sufficient... The response <br /> is inadequate. As these ponds are part of the required EPP, designs are required <br /> prior to approval of the EPP. <br /> See response to "b." above. <br /> 2. Page ESWMP-5, section 7.2...state the specific design storm depths... "August 1, 2013 <br /> response is adequate. <br /> 3. Page ESWMP-6, last paragraph, DDP Drawing 3 of 7, and FlowMaster output pages. <br /> a. The August 1, 2013 rationale for the selected roughness coefficients response is <br /> adequate. However, the DRMS has revised the February 22, 2013 Attachment A <br /> and disagrees with the use of Manning's n values of 0.035 (stability)for earth- <br /> lined channels. Referencing TABLE 802A, items b.4 and b.5, Manning's n for <br /> unarmored channels should be: 0.025<n<0.028. Please revise the calculations, <br /> or justify using the same roughness value for earth-lined and riprap-lined <br /> channels. <br /> The referenced TABLE 802A indicates Manning's "n"values ranging from 0.025 to <br /> 0.050 for natural channels and for rock-lined channels (see sections b and d). The <br /> ranges are obviously meant to cover variations in conditions for the materials and <br /> methods of construction. It is not surprising, in our opinion, that the ranges are <br /> very similar for both natural and rock-lined channels. In addition, we are using the <br /> fairly conservative approach of using the low ranges (least rough)for calculations <br /> 1 <br />