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III IIIIIIIIIIIII III <br />999 <br />G.T'ATL- r"1~ r~~ It nib A T1~ <br />.J 11 11 L Ul `.~JL~Jl~! 1LJLJ <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman Sr, Room 215 <br />Denver, CO 60203 <br />Phone: (3031 866-3567 <br />FAX: f}031832-8106 <br />Date: November 12, 1992 <br />To: Joe Dudash <br />~~ <br />From: David Berry <br />Re: TBM -Notices of Violation C-92-013 and C-92-014 <br />,~~ °~a <br />Ne : -6 <br />.~(~~4j ~ <br />~1`yy• <br />~ r8]6 <br />Buv Sumer <br />Governor <br />rotichael B. Lonq <br />Division Duecmr <br />I have reviewed the above-referenced violation folders, and the operator's submittals of <br />September 10 and October 18, 1992. It is my understanding that the Notices of Violation <br />were written because pond 15-P1 did not adequately treat disturbed area runoff, and <br />because a ditch leading to pond 15-P2 breached, allowing offsite runoff of untreated <br />disturbed area drainage. The operator contends that both violations should be vacated <br />because the runoff event exceeded the projected 10-year, 24-hour runoff. <br />It is my opinion that if it can be documented that the specific design event for which a <br />structure is sized was actually exceeded, then a violation would not be appropriate. I am <br />not, however, of the opinion that such documentation has been provided. The operator's <br />submittal actually verifies that an antecedent soil moisture condition II existed prior to the <br />event in question. June certainly falls in the growing season, and according to the cited <br />reference, total precipitation of 1 .1 inches during the five days prior to the event qualifies <br />as an AMC II, not AMC III. The observed flows were probably within the expected range, <br />thus the pond and ditch should probably have treated the discharge. <br />I would also argue that the method by which the operator has estimated actual flows is <br />extremely suspect. However, given our probable inability to derive any estimates which <br />are more accurate, his estimates might be given some validity. This issue is probably not <br />relevant, though, since the projected 10-year, 24-hour peak flow in the breached ditch <br />would be closer to 90 to 100 cfs, not the 50 cfs value cited. The ditch probably should <br />have controlled a much larger flow than was actually observed. <br />Finally, all theory manipulation aside, I recommend that we compare the approved design <br />numbers for both the ditch and pond, to the flow numbers provided by the operator. If the <br />actual flows definitely exceeded the previously approved design calculations, then the <br />violations should probably be vacated. If, however, no such finding can be made, the <br />violations should stand. <br />DAB/bjw <br />M:\oss\bjw\dab <br />