As part of Waverly’s Watershed Master Plan, the Ash Hollow tributary was identified as the city’s number one priority concern. The Dam is Waverly’s proposed solution. The Dam is designed to lower the peak flow of the Ash Hollow tributary. The dam would be located south of Waverly.  Overall, the Dam would lower the flow through the tributary and lower the amount of flooding through Waverly.

Per the Ash Hollow Dam Preliminary Design Summary Report, a preliminary opinion of probable costs was determined and compared to the benefits.  The total anticipated project costs including construction, land rights, feasibility, engineering and inspection are estimated at approximately $2,785,000.  The total estimated annual benefits are around $234,500.  The estimated annual operation, maintenance and repair costs are approximately $11,000.  Over the 50 year life cycle the total benefit to cost ratio was computed to be 3.34:1, with a rate of return of 7.40%.  The findings of the preliminary design and study report indicate that this project would provide great flood reduction benefits to the City of Waverly.  The next steps in the process are:

  • Identify funding sources and develop an application,
  • Prepare a detailed geotechnical evaluation,
  • Obtain a detailed topographical survey of the dam embankment and spillway area,
  • Prepare detailed ground water study,
  • Prepare final design plans and specifications,
  • Obtain land rights and permits, and
  • Bid and construct the project.

Olsson Associates has been hired to identify funding sources and to develop an application.  

This project has reached an important milestone.  FEMA has reviewed the application submittal for a Conditional Letter of Map Revision (CLOMR) and determined that the proposed project meets the minimum floodplain management criteria of the National Flood Insurance Program (NFIP).  FEMA’s Conditional Letter of Map Revision Comment Document is their concurrence of ultimate approval of the remapped floodplain, as long as the Ash Hollow dam project is constructed as approved and the final Letter of Map Revision (LOMR) is submitted with the required supporting data.  FEMA’s Approval of Ash Hollow Dam CLOMR


For more information visit the Waverly Watershed Master Plan or read the Ash Hollow Dam Preliminary Design Summary Report