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require extraordinary evidence". The fact that the precipitation amount was based on <br />information provided by a nearby resident (rather than collected on-site by the permittee), <br />and that the storm duration was based on third party estimates rather than on-site storm <br />duration recording, casts some question on the data. <br />Further, we question the accuracy of SEDCAD modeling for a storm duration of 1.5 <br />hours, as included in Jim Stover's submittal, which indicated a peak flow in excess of the <br />design event peak flow for the RSRDA Diversion Segment "B". Short duration storm <br />models are inherently less accurate than longer duration models. The Type II storm <br />model used in the approved permit design delivers 1.1" of rain in approximately 30 <br />minutes on an already wetted surface, so a short duration, high intensity component is <br />built in. Without well documented, site collected data for precipitation amount, storm <br />intensity and duration, the Division relies on the 100 year, 24-hour (Type II) storm event <br />modeling, as included in the approved permit. At the Roadside Portals Mine, the <br />precipitation amount for this design event is 2.2". Unless detailed, site specific <br />documentation is provided to demonstrate higher peak flows, drainage structures are <br />required to function without failure for rainfall events that deliver 2.2" or less within a 24 <br />hour period. <br />Please contact me if you have any questions regarding the enclosed Notice of Violation. <br />Please take note of the specified abatement measures and timeframes. <br />On a related matter, I am aware that maintenance work is on-going at Roadside, to <br />complete necessary maintenance associated with the July 20`h storm event at the site and <br />the August 1 flooding down Coal Creek. If there are any sediment control system <br />breaches still remaining from the July 20 storm event (examples would be the North <br />Portal berm separating Pond 13 drainage from SAE drainage, SAE silt fence breaches at <br />the North Portal and the 016 discharge drill pad, etc.), please ensure that they (and any <br />other such breaches) are repaired/replaced promptly, no later than August 18. The <br />blocked Haul Road 4 culvert at the end of the North Portal West Upper Diversion, and <br />the ditch below the culvert down to Coal Creek is also a high priority item, and should be <br />promptly repaired. I would request that other maintenance and repair work addressed in <br />my inspection reports of August 7 (for problems caused by the July 20 storm) and August <br />9 (for problems caused by the August 1 flooding of Coal Creek), be completed by August <br />31, 2006. Please contact me if you foresee any problems with meeting these <br />deadlines. <br />Environmental Protection-Speciali <br />enclosure <br />C: Denver File (w/enclosure) <br />