Five years after the breach of Lake Delton into the Wisconsin River from unprecedented flooding, the lake and improved Dell Creek dam have weathered well.
Should the floods of 2008 happen again, it is very likely that Lake Delton will not escape again into the Wisconsin River.
“We designed (the repairs and renovations) to make sure it would meet or exceed the event of 2008,” said John Langhans.
Langhans is a team leader with MSA Professional Services of Baraboo, and has worked as the engineer for the Village of Lake Delton for nine years.
“There’s been a lot of design put into effect and we are confident the designs will perform well into the future,” Langhans said.
The bedrock in the area of Lake Delton is relatively high. It is what allows the lake to exist; the waters of Dell Creek are held back by the surrounding bedrock, and its level is controlled by Dell Creek dam.
The lake was formed in 1927 with the completion of the dam; it became the center of Wisconsin Dells tourism, and in 2008, supported 21 businesses, including the Tommy Bartlett show led by Tom Diehl, the Original Wisconsin Ducks managed by Dan Gavinski, and various resorts and vacation homes.
The path of least resistance
Following days of rain, an additional 12 inches of rain fell on the Lake Delton area in the early hours of June 9, 2008; volunteers, worried that the 81-year-old dam would fail, spent hours stacking sandbags along the sides of the dam and removing debris from the front of it as water levels rose to record heights and beyond.
The water kept coming, however, and found a new path of lesser resistance in an ancient creek bed channel, about 500 feet from the current channel where the Dell Creek dam is located.
“Back when the last Ice Age happened, that used to be where the creek went to the river,” Diehl said. “When the glacier receded, it deposited all this sugar sand in the ravine.... It was the old creek bed for Dell Creek before the Ice Age.”
It was filled with nothing stronger than sediment where the bedrock takes a dip.
“Think of it like a big U,” Langhans said.
The water seeped underneath the homes and the trees and Highway A, liquefying the soil. It had already washed out the trail followed by the Original Wisconsin Ducks, a low point in the area.
“That’s where the first breach occurred,” Gavinski said.
With years under his belt as a driver on the river, Gavinski had never looked closely at the area that would become the breach; now, he sees those filled-in voids, the weak points, continuing across the Wisconsin River and as far as the high school.
“That was the drain point 10,000 years ago,” Gavinski said. “If you look around” you can see it.
“I never even looked at it until this happened,” Gavinski said.
Diehl was with Gavinski and watching the water flow over Highway A when he realized just how water-soaked the land was in the area.
“There’s an emulsion here and it’s going to give away sooner or later,” Diehl told Gavinski.
The soil there was now extremely saturated; it was coupled with a fast and high, eroding current in the Wisconsin River, and the weak point was exploited.
Shortly after, 600 million gallons of water, in an uncontrollable torrent, tore away trees, soil, sand and houses and carved a new 400-foot-wide channel. Three houses washed down the river; two others were destroyed when the land underneath was worn away by the receding lake waters.
It took about two hours for the lake to drain away and become lost in the Wisconsin River.
“All it was, was sand... it was a void,” Gavinski said.
Lake Delton is a resource in the area: It is the heart of Wisconsin Dells tourism, and the home of 21 businesses employing hundreds, in addition to being home to many people. The lake and its businesses bring in essential tourism dollars each year to the area and to the state.
“The village (of Lake Delton) had a catastrophic event,” Langhans said.
The lake had to be repaired and refilled as quickly as possible to save those businesses and the tourism industry in the area.
Maybe those businesses would last one summer without its jewel, but not two: Time was of the essence.
A masterpiece of cooperation
Officials came up with an aggressive schedule: Repair the area of the breach, and repair and improve the dam, and do it as soon as possible.
Normally, such projects would take one to two years to complete; this one was condensed into less than six months.
“Everything was fast-tracked,” Langhans said.
It was a collaborative effort of the village — including Diehl as a village trustee — Langhans and his design team at MSA and Mead and Hunt, the Department of Natural Resources and the Department of Transportation, and Gov. Jim Doyle’s office, with help from area sporting clubs.
“It was a superhuman effort from all the stakeholders,” Langhans said. “There were a lot of players in this game. And everybody performed exceptionally.”
“Governor Doyle did a marvelous job, setting the tone from the get-go,” and discouraging inter-agency squabbling, Diehl said.
They used a new project strategy: Get the work started, then plan additional phases while the work is going on. It was vastly different from the typical way to run a project, where the plan is developed beginning to end well before work begins.
Very different: they didn’t have time. But it worked.
“It was a very successful model,” Langhans said.
The effort was an example of the best type of cooperation.
“Without the public/private partnership, this project could not have happened the way it happened,” Langhans said.
A cofferdam was quickly built to divert the Dell Creek water away from the area of the breach and back toward the dam.
In the area of the breach, they got to work; about 12,000 truckloads of fill were brought in, with trucks going back and forth day and night.
They added a second dam to the lake, the first of its kind used in Wisconsin: a four-foot-wide slurry wall, using Bentonite clay, wider than the gap of the breach.
“It slowly sets up and forms a seal... like caulk,” Langhans said. “We’re trying to stop the subsurface flow of water.”
They added a specially-engineered fill, and lined it with riprap — the large rocks embedded in the soil to prevent erosion.
At the same time, improvements were made to the dam, allowing it to handle more water and easily handle a similar flood event in the future, Langhans said.
The endangered sewage lift station in Kaminski Park was stabilized, and water and sewer lines rerouted through the area affected by the flood.
To help with fishing in the lake, the DNR eradicated carp — a nuisance fish that degrades water quality; they also got rid of nuisance weeds, and plans were made to leave the cofferdam and other areas in the lake provide for fish spawning grounds.
The village spent more than $1 million in correcting how sedimentation was coming into the lake, Diehl said.
A new park was created in the area of the breach; it now has a handicapped-accessible fishing pier.
With the final slurry pour in early December 2008, the lake was filled halfway for the winter; and business owners like Diehl began to have hope.
Better than ever
In April, with everything done, they shut the gates on the dam and let the creek bring the water in. It did not take long for Lake Delton to make its reappearance.
“Mother nature took care of it for us,” Langhans said.
The lake was restocked with fish; the water came back and stayed clear enough to see the bottom.
“The fishing has been improved; the water quality has been improved (and) the ability to handle large storm events has been improved,” Langhans said.
“The lake and the dam have performed outstandingly well with all post-2008 events,” Langhans said. “There have been absolutely no problems.”
“That dam can now handle a thousand-year storm,” Diehl said.