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 designed to lower the peak flow of the Ash Hollow tributary, and is located south of Waverly. Overall, the Dam has lowered the flow through the tributary and lowered 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 was 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%.
FEMA reviewed the application submittal for a Conditional Letter of Map Revision (CLOMR) and determined that the proposed project met 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.