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TR-13, Adequacy 2 C-80-006 4. SEDCAD printouts and hydrology summary tables (pages 23-115, 23-115a and 23- 154) were submitted for ditches PD-3, PDT, PD-5 and culvert PC-3. Hydrology data states that ditches PD-3, PDT, PD-5 and culvert PC-3 have all been designed to safely pass the 100 year, 24 hour event; however, Table 23-18 indicates that culvert PC-3 is designed for the 10 year event even though the peak flow listed is that of the stated 100 year event. Table 23-18 also suggests that culvert PC-3 is a single 24 inch diameter pipe rather than two 24 inch diameter pipes. Please m..Ll_ if i /-,,, 1 A C A7\ a tote t t 3 1 f r IeVIJe aaulc ~3-~8 ~Yage ~3-15~ c. Exhibit ~~~ .c s ha PC- :s designed e the 100 year, 24 hour event and to state that PC-3 is actually two 24 inch diameter pipes. S. As stated above, SEDCAD printouts and hydrology summary tables were submitted for ditches PD-3, PDT, PD-5; however, the submitted data did not include channel designs for the three ditches. Please submit specific designs for ditches PD-3, PD-4 and PD-5. 6. Page 23-151 of Exhibit 42 of the permit was revised to state that ditches PD-3, PD-4, and PD-5, are shown on Map 16A and Map 37A. Map 16A was not included with the TR-13 application packet. Please submit an updated version of Map 16A, Mine Area Surface Water Hydrology, which shows the location of ditches PD-3, PD-4, and PD-5, culvert PC-3 and the final topography of the Pit 1 area modified under TR-13. 7. Removal of 27,000 cubic yards of road fill in Bush Draw will eliminate the access road to Pond G and its associated topsoil stockpiles and sediment containment ditches G-1 and G-2. Please address how access will be secured for maintenance and reclamation for these structures. Please contact me if I can be of greater service. Sincerely, Wallace H. Erickson Environmental Protection Specialist cc: Jerry Nettleton, TerraMatrix, Steamboat. Thomas Leidich, TerraMatrix, Lakewood.