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4. On Figure 1 it appears that the label for the old underdrain location was Ieft on the <br />drawing by accident. Please explain or revise your submittal. <br />Rule 4.10.3 — Water Control Measures for Coal Mine Waste Banks: <br />5. Regarding the underdrain design, please address the following and revise your submittal <br />as appropriate: <br />a. Why is the new cross section smaller than the existing one? (Three square feet <br />rather than four square feet.) <br />b. PIease elaborate on the location of the proposed upper end of the underdrain. <br />c. Explain why the last 20 feet of the underdrain pipe will not be solid as in the <br />previous design. <br />d. Please explain the slope used in the calculation. Is it based on the slope of Ditch <br />D -J 10? <br />This concludes the Division's adequacy review of Technical Revision No. 114. If you have any <br />questions, please feel free to contact me at (303)-866-3567 x 8144. <br />Sincerely, <br />Clayton Wein <br />Environmental Protection Specialist <br />clayton.wein@state.co.us <br />oF'Co <br />I555 Street Address, Room 555, Denver, CO 55555.5555 P 555.555.5555 y � 0 <br />} 1876 + <br />