Lower Beaver Brook Dam

May 8, 2015 by  
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Unusually sustained precipitation coupled with normal spring snowmelt in the Beaver Brook Watershed has resulted in higher than normal flows in Beaver Brook.   The State Engineer’s Dam Safety Branch requires monitoring under certain conditions, including extreme weather events, higher than normal flows through the Lower Beaver Brook dam spillway and a higher than normal pool level.  Under the Dam’s existing Emergency Action Plan, the Lower Beaver Brook Dam is currently being monitored at a Level 1.  This is a precautionary Level and does not indicate deteriorating conditions to the dam itself.  The dam’s crest is not designed to “overflow” or “overtop” and overtopping should be avoided.  If the spillway cannot adequately pass an unexpectedly large flow, the dam crest could be “overtopped.”  The District is doing everything possible to maintain dam safety under the Emergency Action Plan and is in compliance with the State Engineer’s direction.

The District had a window of time between the first heavy rains on Tuesday and the expected precipitation later in the week in which sand bags were placed to increase the freeboard (freeboard is the distance between the pool level and the dam crest).  Having more freeboard creates a greater margin in order to avoid an overtopping.  The sand bags do not alter the amount of water that can be stored on a permanent basis, nor control the water entering or leaving the spillway.  The extra barrier provides a safety buffer, and would serve to channel water in the pool toward the spillway at approximately the same rate as the inflowing beaver brook water, should the water pool reach the original dam crest elevation.

Recent events have caused concern to residents in Beaver Brook Canyon, especially those who experienced flood damage in September of 2013.  In 2013, types of damage included culverts that were overwhelmed, severe damage to bridges, damage to structures, and severe damage to public and private roads and driveways; utilities were also damaged and access to property was restricted.  The District had over $100,000 in property damage and many thousands of dollars of other types of mitigation costs.  During the extreme weather events in 2013, the Lower Beaver Brook Dam was also monitored at a Level 1.  The County as a whole was included in the federally declared disaster areas in Colorado and FEMA became part of our everyday conversation.

We have chosen to be located in a natural “funnel” at the bottom of a 5,120 acre drainage basin, known as Beaver Brook Watershed.  We often find ourselves worried about water shortages, but this time it is the opposite.  Fortunately, this time around residents are more informed and aware, and some property has been improved during or after the 2013 flood mitigation occurred, and can now withstand greater flows within Beaver Brook.