Winter Inspections
We first shared this article in our January 2019 Dam Safety News. But since winter is arriving soon, this is a great time to revisit how to inspect your dam during the season.
When winter arrives in Wisconsin, impoundments will eventually become ice-covered. So, there is no need to check on your dam until springtime, right? Wrong. Water works on and against dams every minute of every day, all year long, including during the cold winter months.
As the owner of a dam, you should still check on your structure even during the winter months to observe its performance. Here are some winter dam inspection tips:
Check for and address debris build-up around the primary control structure year-round. As fall transitions to winter, tree leaves and other organic matter from around the impoundment naturally flow toward the dam's spillway. A build-up of this material in the spillway can reduce its ability to pass water efficiently. If a build-up of this material freezes in or around the spillway, this has the potential to reduce the hydraulic capacity of the spillway and may lead to overtopping and possibly failure of your dam. Having pike poles, gaff hooks or debris rakes readily accessible to you during your inspections is crucial for clearing debris away from your spillway structures.
Walk the earthen embankments of your dam and look for signs of seepage or instabilities of the earthen slopes. Before snow becomes deep, seepage areas are readily visible because the relatively warm seepage water melts shallow snow in areas of active seepage. Monitor these areas and flag them as areas of interest during subsequent inspections for changes in size and flow volumes. Report cloudy seepage water to your consultant and regional DNR dam safety engineer as soon as possible. Also report any observed slope instability, such as scarps, slides or areas of excessive settlement.
Check the condition of all spillway components during each inspection. Dam construction by a beaver is likely to occur around inlet structures any time of the year. Dams that have fixed crest spillways or rock-lined channels as a primary control structure are particularly susceptible to beaver dams being constructed that may obstruct flow and result in changes to the impoundment's depth and size. You can find guidelines to help solve nuisance wildlife problems on our DNR dam safety website.
Routinely inspect dams with gated spillways to ensure that ice build-up will not interfere with operation of these components should a winter rain event or sudden warm-up with run-off occur. You may want to have a steam cleaner available to keep gates ice-free and operational during the winter months.
Remember, inspections of your dam are just as necessary in the winter as they are during other times of the year.
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