After Wisconsin dams failed in a massive storm, 23 could be decommissioned. What to know.

VIROQUA - Local officials in a flood-prone pocket of Wisconsin's Driftless region are weighing whether to take 23 flood control dams out of service.

In August 2018, five of the dams failed during a massive rainstorm , sending a deluge of water gushing through the valleys. A study of other dams in the area found several more were also at risk.

In Vernon County — home to the majority of the dams examined in the study — county board members voted Thursday to take a step forward in the process, securing federal funding for the project and greenlighting the U.S. Natural Resources Conservation Service to begin designing what the decommissioned dams might look like.

The plan to dismantle the dams has drawn mixed reactions from the public. Some see it as a necessity to prevent future catastrophes, while others are nervous about what largely unchecked floodwaters could do to downstream properties that have been protected by the dams for decades.

Residents who spoke at Thursday's meeting, along with some county board supervisors, raised such concerns. The vote to move forward with the design process passed with heavy emphasis from county staff that it doesn't preclude a later decision to keep some of the dams down the road.

"If we're very likely to decommission a good number of them ... let's get the money, let's get the design," said Vernon County conservationist Ben Wojahn.

The plan for the dams is a historic one for the area, which has a long history of pioneering conservation work aimed at protecting its unique landscape. Residents say recommitting to that work could help them learn to live without the dams — and that other communities with aging dams can start exploring it too, particularly as climate change brings more frequent and severe floods that threaten to overwhelm them.

"A national conversation is needed here," said Nancy Wedwick, president of the Coon Creek Community Watershed Council. "Because, boy, we're the first, but we're not alone."

Here's what to know about the dams, what led up to this point and what could come next.

Where are the dams?

After the 2018 breach, federal officials launched a study of all of the dams in the Coon Creek and West Fork Kickapoo watersheds , where the failures occurred. Those watersheds are largely in Vernon County, but include some of the southernmost parts of La Crosse and Monroe counties too.

During the storm, three of the Monroe County dams failed, as well as two in Vernon County. Those include:

• Luckasson Dam
• Blihovde Dam
• Korn Dam
• Mlsna Dam
• Jersey Valley Dam

Work to decommission Mlsna Dam has already started, using state grant money.

PL-566 dams were built decades ago; a third have 'high hazard potential'

The dams were constructed in the 1950s and 1960s by the Natural Resources Conservation Service, a division of the U.S. Department of Agriculture, as part of a nationwide project to control floodwaters in smaller watersheds .

Picture a dam, and these ones likely aren't what you're thinking of. They're made from the earth, are covered in grass and stand around 30 feet high.

Moreover, most of them are dry dams, meaning they don't hold back a pool of water, but instead stand at the ready to hold back floodwaters during heavy rains.

The dams are known as PL-566 dams because they were a product of Public Law 83-566 , in which the federal government paid for the structures in return for a "local sponsor" — in this case, the three counties — becoming legally responsible for them. The counties also had to get farmers upstream of the dams to use conservation practices on their land that would help hold water and soil on the fields instead of sending it downstream.

There are currently 7,779 of these kinds of dams across the country, according to a Natural Resources Conservation Service spokesperson, including 80-some in Wisconsin.

About one in three nationally are classified as having a high hazard potential , which means dam failure could cause loss of life and significant property damage. (That's not a remark on their condition, which can range from "satisfactory" to "unsatisfactory." )

5 Wisconsin dams failed in catastrophic 2018 storm, causing millions in damage

Southwest Wisconsin is no stranger to the problem of flooding. The flashy Kickapoo River, a tributary of the Wisconsin River, has jumped its banks several times throughout history, leading to major flood damages that even prompted some communities to relocate to higher ground . The steeply sloped topography that defines the Driftless region also makes water coursing over the landscape run faster.

But the storm that hit the night of Aug. 27, 2018 , proved to be the most catastrophic yet. Up to 12 inches of rain pounded the area over just a few hours — in the biggest raindrops Wedwick said she'd ever seen in her life — bursting through the sandstone of five area dams. Residents say it was a miracle no one was killed.

Mark Erickson, Vernon County resource conservationist, remembered getting the call that the Jersey Valley dam — one of the few that held back water to create a lake — had failed. When he got to the scene, all he could do was watch the torrent. Tree-sized clay masses from the dam were falling and being rushed away.

"I just couldn't believe it," he recalled.

In Vernon County alone, the flooding caused an estimated $29 million in damage .

Study found all area PL-566 dams at risk, not cost-effective to rebuild

Many people wanted to have the breached dams immediately repaired after the storm, said Steve Becker, Wisconsin's state conservation engineer for the Natural Resources Conservation Service. But the agency urged a deeper analysis of how all the PL-566 dams in the two watersheds had performed over the past few decades and how they could perform in the future.

Becker said the analysis found that in retrospect, most of the dams had done great. The future, on the other hand, didn't look so good.

All of the dams had what Becker called a "geotechnical vulnerability to failure": they were built on the fractured sandstone of the Driftless region, which engineers at the time of construction didn't take into account. At the dams that breached during the 2018 storm, he said, water seeped into those fractures to move around and underneath the dams and eventually washed them out.

"If the storm would have lasted longer, or if we were to get another storm of the same magnitude, there's a high probability we would lose other dams," Becker said. But the cost to repair them would be steep — a few million dollars apiece — outweighing the dams' benefits, by the agency's analysis. Staff recommended decommissioning them all, and offered to cover nearly all the cost of doing so.

Only Jersey Valley Dam was recommended for replacing, because the lake it held back before it breached was popular for recreation.

What happens if the dams are decommissioned?

If the counties move forward with decommissioning, the dams would not be removed from the valley floor completely. Instead, they would each get a U-shaped notch cut out of them, enough to let a sizable flood pass through unimpeded.

Ownership of what's left would likely be returned to the people who own the land the dams are on.

In public comments on the draft plan to decommission the dams, concerns were raised about loss of habitat for brook trout and the potential for the notched dams to still pose a safety risk if they are damaged in future storms. American Rivers , a nonprofit environmental group that advocates for dam removals, wrote in a letter that "a notched dam is a missed opportunity to restore the natural ecosystem, especially where so much funding is available for dam removal and river restoration."

Becker said the decision to notch the dams instead of remove them came down to cost, and that removing them would have been almost as expensive as rebuilding. He also said the smaller size of these dams will mean the notch will greatly reduce that size.

"By the time we take this notch out, what's left isn't going to look any different than all the hills and valleys of the Driftless," Becker said.

Are there options other than dams for slowing floodwaters?

In absence of the dams, landowners could take steps to slow water down when it falls on their properties, like planting perennials and rotationally grazing livestock. It's something Wedwick feels area residents are uniquely positioned to do.

The Coon Creek watershed was the site of the nation's first large-scale demonstration of soil and water conservation , which began 91 years ago this October. And the Coon Creek Community Watershed Council, which formed to help residents build resilience after the 2018 flood, has a goal of "making running water walk," so more of it sinks into the earth and less flows downstream.

There are disagreements over how much impact widespread land conservation practices could have on slowing particularly large floods, and hesitance over whether enough landowners would voluntarily adopt such practices. Wedwick said she feels the Natural Resources Conservation Service study didn't give enough credence to the idea that landowners would do so. She offered the conservation project that began 91 years ago as an example: it wasn't easy to convince people then to improve their farming practices to curb soil erosion, she said, but it got done.

Wojahn, the Vernon County conservationist, said he's hopeful that the county can procure more funds — and more staff — to implement conservation practices to slow water down. He called on the region's elected officials to help them find creative ways to build resilience across the landscape.

How much will decommissioning the dams cost?

It will cost about $4.4 million to decommission the 14 dams in the Coon Creek watershed , about $7.7 million to decommission nine in the West Fork Kickapoo watershed, and about $17.8 million to replace Jersey Valley , most of which will be covered by NRCS.

Wojahn said prior to Thursday's meeting while there's no formal deadline after which the county would lose that federal funding, a presidential administration change or other political headwinds could put it in jeopardy, and that a decision needs to be made sooner rather than later.

"Some people have said it's being rushed, but 2018 was quite a while ago," Wojahn said. "We do need solutions, especially for the breached (dams). They can't just stay like that."

Do residents support decommissioning the dams?

In La Crosse County, which would have two dams decommissioned, and Monroe County, which would have seven, residents have been supportive of the proposal, said Matt Hanewall and Bob Micheel, who direct each county's land conservation department. The Monroe County board is expected to vote on the dam decommissioning resolution Aug. 28, and in La Crosse, Sept. 19.

Some Vernon County residents have been more leery. There aren't many properties in the two to three miles downstream of the dams, Becker said, but they'll hurt the most — the structures allowed them to plant cropland, and protected county roads that otherwise might have been washed out. Especially if people live behind a dam that hasn't failed, he said, they might be averse to getting rid of it.

Wedwick worries that too many residents still don't know the dams are being decommissioned, and that the study's cost-benefit analysis didn't fully represent human interaction with the dams.

"To say, 'Well, they're not protecting enough in order for them to stay,' that's a little hard to handle when what they're protecting, maybe, is your home," she said.

Madeline Heim is a Report for America corps reporter who writes about environmental issues in the Mississippi River watershed and across Wisconsin. Contact her at 920-996-7266 or mheim@gannett.com .

This article originally appeared on Milwaukee Journal Sentinel: After Wisconsin dams failed in a massive storm, 23 could be decommissioned. What to know.