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20 Photo 1: Aerial image of UEV and LEV Dams. Based on post-failure survey data, the UEV Dam was estimated to have a maximum height of 12 feet and storage capacity of approximately 6.4 acre-feet. The LEV Dam was a larger structure, with an estimated maximum height of 14 feet and storage capacity of approximately 11.4 acre-feet. Post-failure inspections of the UEV Dam identified at least eight pipelines penetrating through the embankment and ranging in diameter from 8 to 30 inches (see Photo 2). The pipe penetrations were the only means for releasing inflows from the reservoir, since the UEV Dam did not have an emergency overflow spillway. Additionally, a septic tank was observed embedded within the left abutment of the embankment with pipelines extending parallel to the dam crest to a leach field on the right abutment. It was also observed that the dam crest elevation was not uniform along the length of the dam and contained several low areas. Photo 2: UEV Dam post-failure looking upstream. Similar to the UEV Dam, post-failure inspections of the LEV Dam revealed the dam crest elevation was not uniform along the length of the dam and contained several low areas. Post-failure inspections also indicated the dam was constructed on a timber foundation to support the embankment over organic foundation materials with a timber cutoff wall constructed below the core of the dam. The principal spillway for the LEV Dam was a 3-foot-diameter corrugated metal pipe (CMP) drop inlet located near the left abutment. It is unknown if a trashrack was installed at the inlet to the pipe. An emergency spillway also consisting of a 3-foot-diameter CMP was found near the right abutment. The elevations of the principal and emergency spillways are unknown, but it is likely the emergency spillway was higher in elevation than the principal spillway and would only be active in large floods, such as the September 2013 storm. An 18- inch diameter steel low-level outlet was observed near the central portion of the dam, but it is unknown if the outlet was operational or had a trashrack. In 1997, the LEV Dam had reportedly failed. The downstream slope in the area of the breach was reconstructed with a relatively steep slope compared to other areas of the downstream slope that were fairly gentle. Aerial photos indicate the 2013 failure occurred at the same location as the 1997 failure. The LEV Dam repairs completed in 1997 may have contributed to the 2013 failure of the dam, considering the relatively steep reconstructed downstream slope in the area of the failure. It is also likely the timber foundation was also not repaired. Photo 3 below shows the LEV Dam post-failure. Photo 3: LEV Dam post-failure looking upstream. According to an eyewitness account, the LEV Dam overtopped and failed first, followed by overtopping and failure of the UEV Dam. Hydrologic modeling UEV Dam LEV Dam