Boxelder B-2/B-3 Watershed Plan

Frequently Asked Questions
This page presents common questions about key aspects of the project with answers from the project team. When we receive an important question in a meeting or in feedback, we’ll post it with an answer here.
We welcome feedback about this project from interested parties within the watershed any time during the May 2015-April 2016 planning study.

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What modifications of the dams will be required?
Evaluations are still being conducted related to the magnitude of the appropriate design flood and modifications that will be required at one or both dams. However, it is probable that some modifications to the spillways and/or embankment will be required. The extent of these modifications will be determined during the alternatives assessment and preliminary design phase of the project. The dams may be decommissioned if sufficient funding to accomplish spillway modifications is not available.
Who will pay for any modifications that may be required?
Funding for the project modifications is not known at this time and is a function of the findings of the Supplemental Watershed Plan and the magnitude of the modifications required. It is envisioned that grants and Federal government funds will be applied for to offset some of the project costs. However, other funding sources may need to be evaluated and pursued.
What would be the impact of decommissioning the dams?
Decommissioning of the dams would reduce the flood reduction benefits of the lower magnitude flooding events resulting in higher peak discharges and potential for flooding in downstream areas.
Why has the hazard classification been raised? Is the dam safe?
The hazard classification is assigned by the Colorado Division of Water Resources/Dam Safety Branch. The High hazard classification for both dams B-2 and B-3 is based on the conclusion that a dam failure would have potential to cause “loss of life, serious damage to homes, industrial and commercial buildings, important public utilities, main highways, or railroads.” A Significant hazard dam is “located in predominantly rural or agricultural areas where failure may damage isolated homes, main highways or minor railroads, or cause interruption of use or service of relatively important public utilities.” The High hazard classification does not mean that the dam is unsafe in normal operating conditions and for lower magnitude flooding events. It simply means that the spillway needs to pass a larger, less-frequent storm event.
Are the dams effective at minimizing the potential for flooding downstream?
The dams are very effective at reducing flooding during events with magnitudes less than the 1-in-100- years event. Peak flows are reduced by over 95% as a result of flood attenuation with the dams during the 100-year frequency event.