Coon Rapids, Minnesota
Estimated Cost: 
$ N/A
  • Dam Built in 1913, Rebuilt 1997
  • 10 Control Gates
  • 13 Foot Waterfall
  • 2,150 Feet Overall, 1,000 Feet Structural
  • High Flow Velocity /Low Visibility

In 2009, 2010 and 2011, AMI Consulting Engineers, P.A. provided Stanley Consultants sector scan imaging inspections of the Coon Rapids Dam. The intent of each project was to complete imaging and dive investigations to identify current conditions and report any changes to the Dam Aprons over time.

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

In 2011, AMI completed the scanning and provided additional video documentation and condition assessment of all previous structural repairs in the low visibility environment.