The Lake Delhi dam, which pooled water above it on the Maquoketa River, has a cement-constructed spillway in the center and earthen structures on either side. The record flooding caused water to go over the dam, and then the south portion of the levee experienced a major breach.
"I've never seen anything like it," said DNR Environmental Specialist Tom McCarthy, who was on the scene.
McCarthy said the road over the dam began collapsing at approximately 1 p.m. as the water cut a 30-foot wide swath on the south side and began cascading more than 40 feet to the Maquoketa River below.
Boats and propane tanks were flowing through the dam breach, said McCarthy, as he watched a newly constructed, hoop-style Delaware County maintenance shed falling into rushing water shortly before 2 p.m.
"I've seen fully grown trees washed downstream in less than a minute," said McCarthy.
Despite the extensive damage caused
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Jack Klaus, a spokesperson for Delaware County Emergency Management, said there have been reports that between 300-700 of the 1,000 properties in the Lake Delhi area have sustained damage. The figure includes everything from minor water damage to complete destruction. Officials are working to gather a comprehensive list of properties damaged, according to Klaus.
The county was spared additional damage when the water surge that resulted from the dam's breach "lost its energy" before it reached downriver, in Hopkinton, Klaus said.
"When it came through the dam, (the water) was ripping, tearing and snorting," Klaus explained. "It did get to Hopkinton. The volume was there, but without the velocity."
Dyersville resident Kori Mahoney, whose family owns a residence at Lake Delhi, said she arrived at the dam site just in time to see it breach.
"It was surreal," Mahoney said. She said among the items she saw go over the dam included a propane tank, which exploded after making it past the structure.
While the Mahoney's property sustained damage as a result of the flooding, the family's boats survived the flooding.
"We feel lucky," Mahoney said.
The Lake Delhi dam was last fully inspected by the DNR in May of 2009, and although a few minor repairs were still needed to be made following the flooding of 2008, no major structural problems were found on the dam, said Lori McDaniel, supervisor of the DNR's flood plain and dam safety section.
"There really isn't much that can be done when we get into an extreme situation like this where water over-tops the structure. The water is just too strong to hold back at that point," said McDaniel.
Meanwhile, Gov. Chet Culver was in the area, July 25. Prior to his arrival in Delaware County, the governor activated the National Guard to the area. He also activated the state Emergency Operation Center out of Camp Dodge.
While the nine-mile-long lake drained in less than a day after the dam breach, the governor vowed to restore Lake Delhi.
Culver said it's in Iowa's best interest to save the lake, calling it a "real landmark." The governor is proposing turning the dam into a modern hydroelectric facility.
"I hope we can consider looking at a new 21st century hydroelectric dam that could help our state in terms of our focus on renewable energy and maybe allow those folks living in Delaware County and there at the lake to provide their own power because of the new hydroelectric dam," Culver said on the Iowa Public Radio program, "The Exchange."
The Emergency Management official also noted that numerous rural homes, from Dundee to Hopkinton, also sustained flood damage.
- The Associated Press contributed.