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Table 2 - Physical Descriptions of Big Elk Meadows Dams and Reservoirs <br />Geometry <br />Sunset <br />Dam <br />Rainbow <br />Dam <br />Willow Dam <br />Mirror Dam <br />Meadow <br />Dam <br />Spillway Elev. (ft) <br />7526.1 <br />7516.2 <br />7509.5 <br />7499.4 <br />7489.9 <br />Dam Crest Elev. (ft) <br />7530.1 <br />7518.9 <br />7515.0 <br />7502.6 <br />7497.6 <br />Dam Crest Length (ft) <br />448 <br />300 <br />256 <br />270 <br />265 <br />Upstream Toe Elev. (ft) <br />7520.1 <br />7506.2 <br />7499.5 <br />7489.4 <br />7481.4 <br />Normal Storage (ac -ft) <br />11.42 <br />37.20 <br />26.67 <br />18.16 <br />32.2 <br />Maximum Storage (ac -ft) <br />19.26 <br />48.99 <br />59.59 <br />29.91 <br />90.38 <br />Normal Pool Surface Area (ac) <br />2.24 <br />6.07 <br />5.35 <br />3.39 <br />7.20 <br />Maximum Pool Surface Area (ac) <br />3.00 <br />6.92 <br />7.06 <br />6.44 <br />11.70 <br />8 FAILURE EVENT AND EMERGENCY RESPONSE <br />Emergency warnings and notifications broadcasted during the early morning hours of September <br />12, 2013 provided the first indication that heavy rainfall was occurring in the area of the BEMA <br />dams. The first warning of flash flooding was issued by the Larimer County emergency manager at <br />12:58 a.m. on Thursday, September 12, 2013. Between 1:00 a.m. and 2:00 a.m. a Larimer County <br />Sherriff's Deputy dispatched to the area became trapped in Big Elk Meadows when the access <br />road (Larimer County Road 47) was washed out and became impassible due to the flow in the <br />Little Thompson River. At 2:11 a.m., the Larimer County Emergency Manager issued a notice <br />specific to Big Elk Meadows reporting critical flash flooding was occurring with possible small dams <br />breaking. A reverse 911 call went out all BEMA residents warning them of the danger. Figure 5 <br />shows an image of CR 47 taken just before 7:00 am on September 12, showing the flooding <br />damage to the road that resulted in isolation of the Big Elk Meadows Community in the first hours <br />of the storm. <br />Subsequent reports and telephone communication with BEMA residents and emergency services <br />personnel over the next 24 -hours communicated that by 7:00 am on Friday, September 13, 2013 <br />all five BEMA dams had overtopped and failed. There was no access to the dams and reports were <br />relayed by residents and first responders. Table 3 presents the timeline of the dam failures as <br />reported by eyewitnesses, some of whom were first responders on- scene, and from review of <br />photographs and videos taken by eyewitnesses. <br />Table 3 - Jurisdictional Height and Time of Failure of Big Elk Meadows Dams <br />Dam Name <br />Jurisdictional Height (ft) <br />Time of Failure (MDT) <br />Sunset Lake <br />6 <br />Sept. 12, 7:41 a.m. <br />Willow Lake <br />10 <br />Sept. 12 12:02 p.m. <br />Rainbow Lake <br />10 <br />Sept. 12 12:24 p.m. <br />Meadow Lake <br />10.1 <br />Sept. 12 1:40 p.m. <br />Mirror Lake <br />10 <br />Sept. 13, Approx. <br />Note: Failure times provided by BEM Fire Dept. log, and Larimer County Sheriff video. <br />Report of the September 2013 Little Thompson River Flooding COLORADO <br />and Big Elk Meadows Dam Failures, June 2014 (Revised, Dec 2014) A&V Division of Water Resources <br />Page 10 of 48 - - <br />■ 9go rm:1ovilU41:1 <br />