Did you know that in the state of Ohio over 30% of dams are classified as high-hazard?
High hazard dams are dams that, according to FEMA, are “...based on the probable loss of human life and the potential for economic losses, environmental damage, and/or disruption to lifelines caused by failure of mis-operation of a dam or its appurtenances.” Placing dam on the high hazard list doesn’t mean that it is necessarily in danger of failing, it simply means that there could be catastrophic consequences if it did fail. This being said, these dams often have rigorous inspection and maintenance programs in place to assure that a dam failure be avoided. For homeowners with smaller dams and levies on their ponds or lakes it is also important that they realize the risk in building and maintaining a dam. It is your responsibility if there is any damage related to or caused by a dam failure. Further information and resources related to dam safety from the Ohio Department of Natural Resources can be found here.
Dams should be inspected regularly, on a yearly basis, and after or during large rain events. When looking at the face of dam owners should look for cracks, sinkholes, slips, and any vegetation other than grass. It is recommended that any shrubs or trees growing in, on, or around dams be removed immediately. Roots from large woody species such as willows or honeysuckle can cause dams to leak and eventually fail. The roots allow for capillary action to take place and provide a space for water to travel. Weed eating should occur once a month to keep these plants from growing. Dams should be free from vegetation and also mowed often for similar reasons. Older dams should be watched more closely, as dams typically have a lifespan of about 60 years, though with proper maintenance and construction they can often last much longer. Some dams may need to be repaired with a new "key" to prevent water from percolating through the dam material. Dam keys are often made from clay or in extreme cases, concrete can be used.
For new dam slopes the grade should be no greater than 2:1. A slope of this size allows for easy maintenance and mowing of dam surfaces. Older ponds with steeper slopes can be modified to accommodate mowing equipment to make it both easier and safer to maintain dam slopes regularly. Mowing should occur every 2 weeks, allowing the grass to become longer will allow for more rigorous root systems to better hold soil in place. Great care should be used when selecting and compacting fill material that is going to be used for your dam. Landowners should avoid building structures on dams and in some cases should avoid driving on them with heavy machinery. Each of these actions can compromise a dam's structure and lead to leaks and potential failure in the future. A brief synopsis of pond construction can be found here.
Dam construction and maintenance can be a daunting and sometimes frightening task. Though with proper planning and management, you can lift the burden of further problems down the road off of your shoulders. Butler Soil and Water Conservation District has many resources and advice for residents wishing to build ponds on their property and is prepared to answer any questions residents may have related to construction and maintenance, please contact our office today at, (513) 887-3720.