COON RAPIDS DAM

Coon Rapids, Minnesota

Initial imaging and dive inspections were completed in 2009 as a baseline inspection to determine the exact extent of suspected apron failure and ensure previous repairs remained intact. As a result of high flow velocity and low visibility of this river, Nordic had to work with dam operations to cycle gates, which minimized the effects of the high flow and produced the best quality images possible. When damage and scour was identified, Nordic mobilized its commercial hard hat dive team to assist AMI Consulting Engineers in the placement of the imaging equipment inside the collapsed sections of the apron to determine the size and volume of scour.

Due to pending plans to add a fish barrier at this site, the decision was made to continue monitoring the damaged areas from year to year until the new construction could correct the apron defects. To limit additional damage and scour, the gates remained closed in this area during normal dam operations and only opened for emergencies.

Annual scanning was completed, provided additional video documentation and condition assessment of all previous structural repairs in the low visibility environment.

In 2013 & 2014, Nordic completed repairs to the dam aprons, gates and hydraulic jumps that were not part of the new fish barrier. Work included crack injection, underwater concrete forming, reinforcement, forming and pumping, repairs to gate systems, debris and sediment removal and general contractor support.