Laserfiche WebLink
approximately 13.2 river miles to a surveyed cross section downstream of the X Bar 7 Ranch. The <br />study area was established to assess flooding damage observed on the stretch of the Little <br />Thompson River through the residential properties in the Pinewood Springs, X Bar 7, Stagecoach <br />Trail, Blue Mountain Road and Ponderosa Hill areas. <br />As is described later in the report, an aerial reconnaissance of the Big Elk Meadows dam failures <br />was made five days after failure, and detailed surveys were conducted 12 days after failure. The <br />intent of the aerial reconnaissance was to determine if the dams had fully breached and a hazard <br />no longer existed. The intent of the detailed surveys was to enable future study of these failures <br />for the benefit of the dam engineering community. The results of any future analysis of these <br />failures will be used by dam engineers to better predict dam failures and the potential adverse <br />consequences <br />It is also important to analyze the dam failures and determine if the anticipated impacts were <br />realized. The Big Elk Meadows dams were classified as minor -size Low hazard and NJ dams. If the <br />impacts from failure of the dams were different than expected then the Rules should be revised so <br />that the risk of these structures and other similar Low hazard dams within the State are properly <br />acknowledged and regulated. <br />The Dam Safety Branch response to the September 2013 flooding events created a backlog of <br />work and the forensic analysis of dam failures had to be placed at a lower priority to other ongoing <br />activities. Only minor work had been done with the collected data between September 2013 and <br />February 2014. <br />In February 2014 members of communities near the X Bar 7 Ranch area in southern Larimer <br />County reached out to the Dam Safety Branch for information pertaining to the failure of the Big <br />Elk Meadows Dams and their reconstruction. The group included members of the Little Thompson <br />River Watershed Restoration Coalition (LTRWRC) that were very interested in knowing the effect <br />dam failures had on the overall flooding and damage their community had sustained. That <br />community interaction provided the Dam Safety Branch the impetus to re- prioritize studies of the <br />Big Elk Meadows dam failures and expand the intended study area to assist in answering the <br />questions regarding the sources of damaging floods. <br />The scope of the study included reviewing historic data on the dams, field inspections and surveys <br />of the dams and river floodplain, analysis of the hydrology of the storm event, interviews with eye <br />witnesses, and analysis of the incremental consequences that the failure of the dams had on the <br />downstream floodplain. The limits of the study include the basins above the Big Elk Meadow <br />Dams downstream to the X Bar 7 ranch, as shown in Figure 3. The limits were selected to capture <br />the rainfall and flooding and analyze the impacts downstream of the dams. <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 6of48 .,,,-- <br />■ 9go VM:1ovilU41:1 <br />