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M I'~ • • / F1r. CJilliam A. Bear -;- June 22, 1982 Additional sediment control procedures including, but not limited to, gravelling of the portal bench, grading of the portal bench so that drainage is directed toward the highwall and not over the surface of the bench, vegetative stabili- zation where practical, and a regular schedule for clean up of coal spilled beneath the conveyor at the mine bench should be addressed. . Ditches: Two problens were noted i.~ith ditch designs; high flow velocities and lack o: freeboard in the design. The size of rock riprap for Ditches A and B should be specified. A D50 of at least 6" is necessary for Ditch B. Also, ditch designs should be revised to incorporate at least o.: ft. of freeboard as required by Rule 9.o5.J(6)(b). stipulation No. 2 The response to the potential flooding issue refers to the flood protection afforded by Paonia Reservoir and the minimization o.` .`lood'potential r:hich will be achieved as a result of the Highway Department's relocation. The response states that "special attention wi1Z be given to reconstructing the channel so that flood potential is minimized or completely eliminated." The effects of the channel relocation on flooding (i.e., the flood event that would be contained within the banks of the channelized river) should be explained in more detail. stipulation N'o. 3 The response states that if water is encountered in the workings, it will be routed to a sumo and NPDcs required parameters will be sampled prior to discharging water to the surface. ~, plan drae~~ing should be provided c.~hich shows the location of the sump(s) in the mine workings and details the desicn and capacity of the sump(s). The response should si->ecifically er.nlain ho~o water would be routed to and contained ;:~ithin the sunns, oiven the fact that rLLnir,g is up-dip and water would r,aturallu drain toward the portals. Stipulation No. 9 The response states that a full gear of hudrologic data will be submitted in August of 1983. It should be noted that the annual report required by the stipulation is to be subru.tted each year of the permit term. sti nulatior, IJO. S The response satisfies the requirements of the stipulation. stipulation No. 6 Again, it is noted that the annual report is to be submitted each yea: of the permit term.