A temporary steel construction wall placed at the site to aid installation of the new Lake Delhi Dam failed June 14.
High water flow on the Maquoketa River is being blamed for the incident, during which the steel construction wall broke away from the concrete wall behind it. Heavy rain last week resulted in flash flooding in eastern Iowa.
The area of the failure was about 10 feet wide in a wall that is about 350 feet long.
The original Lake Delhi Dam failed in July 2010 after two days of heavy rain and the lake was drained and has since sat empty.
At the time of the failure, floodwaters were 25,000 to 30,000 cubic feet per second. The new dam and spillway should be able to handle flows as high as 69,000 cfs.
The Lake Delhi Combined Recreational Facility & Water Quality Board made a unanimous decision to rebuild the dam in February 2014.
This work, to be conducted in two phases, included rebuilding of the dam and construction of public access points. Total cost of the project was expected to be about US$16 million.
Before this most recent incident, construction of the replacement dam was scheduled to be complete by the end of October.
The original dam was completed in 1927 and included a small hydropower project until the 1970s. There have been discussions about adding a 1.5-MW powerhouse at the dam, although we are not aware of any decision having been made.