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Figure 6 —A <br />reconnaissance trip to the Big Elk Meadows and Pinewood Springs areas. <br />N�17A LTA IfillILIJ:1V <br />he first <br />Reports indicate that all the Big Elk Meadows dams were overtopping by midnight on Wednesday <br />September 11, 2013. According to eyewitness reports, Mirror Dam was being overtopped by 2 <br />feet of water at 4:00 am September 12. Rainbow Dam was reportedly being overtopping by 3 feet <br />of water at 5:00 am. <br />Reports indicate that Sunset dam was overtopped for approximately seven hours and failed at <br />7:41 am on September 12. Willow Dam overtopped for over 12 hours and then failed at 12:02 pm. <br />Material was washed around the left abutment of the dam into a residence as the reservoir <br />drained through erosion of native material adjacent to the dam. The reservoir emptied with the <br />main dam still standing. Rainbow dam also overtopped for approximately 12 hours and breached <br />at 12:24 pm on September 12, 2013. The discharge from the failure of Rainbow dam was <br />attenuated as it flowed through both the left abutment breach and through a new breach in the <br />weakened Willow Dam embankment immediately downstream. Meadow Dam breached at 1:40 <br />pm on September 12, 2013. As the spillway operated at full capacity, this dam was overtopping <br />continuously for nearly 13 hours. Finally, a low area near the left abutment concentrated flows to <br />the point of full breach initiation. Review of videos of the Meadow dam breaching event and <br />photos taken immediately afterward, indicate a time of 30 to 45 minutes from the time the breach <br />began forming to the when the reservoir was completely drained. <br />Report of the September 2013 Little Thompson River Flooding COLORADO <br />and Big Elk Meadows Dam Failures, June 2014 (Revised, Dec 2014) * Division of Water Resources <br />Page 12 of 48 D pirtm._nt or r.a,ur,r s,,sourc�, <br />DAM SAFETY BRANCH <br />