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STATE OF COLORADO <br />DIV?SI?N OF RECLAMATION, MINING AND AFkTY <br />Department of Natural Resources <br />? 313 Sherman St,, Doom ?? 5 <br />Denver, Colorado 8?2?3 <br />PFrone: (3?3] 8GG-35b7 <br />FAQ: ?303? 832-81 ?? <br />INT??????? IVIE?RAI?? <br />T?: Dan 1Vithews <br />FROM: Mike Baulay <br />I)?TE, October 1, 2aa9 <br />SU?J??T: Seneca II- Permit Na. C-S?-aS7, Technical Rev?slan No. ?7 ?TR??7} <br />Yaast Mine Permit No. -?4-a82, Technical Revision ??. ?? QTR-43} <br />Runoff Control Structures <br />COLORADO <br />DIVISIQN OF <br />REC?AAT??N <br />hr?rNlN?x <br />?AFET? <br />Bill Ritter, fir. <br />Governor <br />Harris D, Sherman <br />Executive director <br />Ronald 1N. Cottony <br />Division Director <br />Natural Resa?arce Tru?t?e <br />Y have reviewed Seneca Coal Company's SCC} responses to au?r adequacy comments for TR-7 <br />and '?R-4? which were submitted ?? SCC to provide design information for proposed runoff <br />control structures at Seneca II- and Yaast Mines. I am recarrirriending approval for these <br />technical revisions; however, please note the following, <br />• SCC has added to the runoff control structure designs an open end T with slatted riser <br />pipe to the bottom of the dan? at the lower pipe and at the upper discharge pipe. As <br />sham in their "typical diagrams" this design should adequately drain the structure and <br />meet our directive to not impound water, SCC has also added a statement to the permit <br />text that these structures will not impound water, .?s such these structures would not be <br />subject to the requirements of Rule 4.4,9. please note that if we find during inspection <br />of these structures that SCC has not installed slotted T risers within, each structure or if <br />we find that these structures are impounding water then a violation is warranted. <br />• we did receive a comment letter from Craig Lis of the office of the State engineer, <br />Divls?on of water Resources CDR} regarding these revision applications. He <br />respo?aded to our completeness letter and his ca?ent was forwarded to SCC. He <br />stated that slow-level outlet capable of draining all storage must be installed an the darn <br />and water .ust be released from the runoff control structures within twenty-four hours <br />or as directed by the division engineer andlor water commissioner, SCC redesigned the <br />structures to r?o? ?n?po?cr?d wa?er? and have slatted pipe from the lowest level of the daxn <br />to the spillway. Further, 1n the event of a storm the maximum capac1ty while draining <br />would be less than ? acre feet. with this redesign these structures will meet the DwR <br />directive as long as they are properly maintained th,roughaut the life of the structure. I <br />office of office of <br />lined (.and Reclamation Denver • Grand Junction i Durango Active ar?d Inactive Mine