The intent of the Safety of Dams rules for new dam construction is to provide minimum standards for design and construction to prevent the loss of life. Compliance with these rules is necessary if your proposed dam meets the definition of a "dam" as specified in the rules.
This definition of a dam is cited in section 74:02:08:01(7) of the rules. In general, a structure is a dam if the height to the dam crest is greater than or equal to 25 feet and the storage at the dam crest (not at the spillway elevation) is greater than 15 acre feet or if the height to the dam crest is greater than 6 feet and the storage at the dam crest (not at the spillway elevation) is greater than or equal to 50 acre feet. The height of the dam is the difference in elevation between the natural bed of the watercourse or the lowest point on the toe of the dam, whichever is lower, and the crest elevation of the dam.
If your proposed dam falls under this definition, then you will need to comply with the safety of dams rules which includes preparation of plans and specifications. A South Dakota registered professional engineer needs to prepare the plans and specifications or, in some cases, the Natural Resources Conservation Service may be able to do the preparation work. Design requirements for the dam are driven in large part by the size of the dam and downstream hazards such as buildings or roads that may be affected if the dam breaches. A preliminary risk assessment of downstream hazards should also be completed as part of the plans and specifications.
Dam Owner Responsibilities. After the dam is completed, the dam owner is responsible for maintaining the dam in a safe condition. Maintaining your dam not only makes sense by protecting your investment but also by protecting you from civil or criminal negligence suits resulting from failure of a poorly maintained dam. Dam failures may be infrequent but they do occur.
Common maintenance concerns are:
Depending on how the dam is constructed, there may be numerous other maintenance items as well. Maintenance inspections should be performed on a regular basis and particularly after a major flood event.
If you have any questions concerning permitting or design requirements, please email us or call the Water Rights Program at (605) 773-3352.