Posted on May 19, 2025
John Reimer oversees Dane County’s Yahara River Sediment Removal Project, a costly years-long initiative to improve water flow and reduce the risk of flooding by clearing sediment buildup in key stretches of the river.
This year, the project expects to complete phase three of a five-phase plan to dredge the Yahara River, focusing on a stretch between Lower Mud Lake and Lake Kegonsa. The next two phases target sections near Stoughton and through Madison’s isthmus.
Dane County purchased a $650,000 Ellicott Dredge for the project, which was estimated to cost $15 million over its lifespan. Underway since 2019, the work followed massive flooding that hit Madison in August 2018 and claimed the life of one resident.
The county has so far removed hundreds of thousands of cubic yards of sediment from the river. Reimer, the assistant director of the county’s Land & Water Resources Department, recently spoke with the Cap Times to discuss the ongoing effort. He discussed its environmental impacts, secondary goals and lessons for future public works initiatives.
What changes have you seen in the environment since beginning sediment removal?
We’ve seen some benefits of the project. We’ve seen some fish down in the deeper water. We’re restoring some of the areas we dredge and adding rock to provide fish spawning and different habitat features. We’ve also seen where we’ve dredged, remarkably, the channel is holding its shape. So we haven’t seen the channel collapse or had any structural issues with the channel.
What did you initially assume about the project that didn’t go to plan?
We’ve been doing dredging for a while since we started our legacy sediment removal project, so there’s a lot of things I’ve come to learn and expect. One thing that was unexpected was some of the variability of the bottom substrates.
Substrate is the bottom mixture of the riverbed. Sometimes we can be working and then there’ll be a rock vein and we’ll need our mechanical dredging. Other times it’ll just be completely sand and then nothing else there. So sometimes it seems a little variable and other times not.
The Yahara River sediment removal project takes place in five phases and six locations. The goal is to remove sediment from choke points along the river to improve water flow and reduce flooding.
How do the Yahara River Sediment Removal Project and the county’s Legacy Sediment Removal Project differ?
They’re different because the Yahara River is a little bit deeper water so we have bigger equipment. In those legacy sediment projects, usually we’re surrounded by wetlands, so we need to use equipment that’s less invasive and won’t have impacts on those wetlands.
The water is also harder to access in those legacy sediment projects because you have to get through a wetland. And then the material we’re dredging is usually different. In the Yahara River, we’re finding more sands and rock, so bigger types of material. In our legacy sediment projects, it’s more silts and clays. Each has different methods for their removal.
What are some of the weirdest things you’ve dredged out of the river?
I’ve heard of a lot of things like scrap metal here and there, bicycles, bicycle rims. They had a bunch of clothes that got clogged on the cutter head once, maybe a bag of clothes was in the water or something. There are a lot of those things that have just been thrown in the water.
How unique is the county’s initiative?
Generally, this is pretty unique. There’s dredging around that people do, usually in places like the Mississippi River or in ports where dredging is typically done for navigation purposes. In our case, the secondary benefit is navigation. Our primary reason is for flow conveyance for flooding. There’s not many cases out there where people are doing that, especially in Dane County and in Wisconsin.
Is there a concern that you won’t be able to keep up with sediment removal, especially if there’s a big rain event before all phases of the project are complete?
By doing the sediment removal, the goal is that if we do get flooding it wouldn’t be as bad without it. There’s still a chance we can get a large rain event and lake levels will go up, but the goal is that this project will limit how high the water would get and how extreme flooding would be.
There’s already been some progress, but really the benefit is when we can get the full connection. Imagine your bathtub fills up with water and it’s got a drain pipe and there’s a lot of clogs along the way. Let’s just say there’s five clogs and you remove four of them. There’s still one clog and it can still back up.
So the benefit here is once we move this fully through the system, remove all those clogs and open up the channel, then the bathtub — or our lakes in this case — could drain efficiently.
Dane County purchased a $650,000 Ellicott Dredge for its effort to remove sediment from the Yahara River and reduce flooding risks.
What metrics are you using to figure out whether the project is successful long term?
There’s gauging stations along the Yahara River looking at water levels and flow. Once we get big storms, we can look at how that flow pattern changes. But since we’ve dredged, we haven’t had a big 2018 flood event. Last year, we had a decent amount of rain, but once we get those big events, that’ll test the system and we’ll be able to see the flow rates, the water levels and make that real world comparison.
Why did Dane County buy its own dredge and hire its own staff for the project?
There were options. We could contract out or we could do it ourselves. What we ended up doing was a little bit of both. The community wanted to see this project happen as quickly as we could. How do we make it more efficient? Well, we could have two crews running. We could hire it out and we could have our own.
Part of having our own crew was knowing that there are some sensitive areas — either with the fish or with historic features — so we wanted to be able to slow down if we needed to or be able to adjust or modify.
Are there any other long-term plans for maintaining sediment removal beyond this current project?
Yeah. When we first started the project, we mapped the underwater topography … so that we know where we’re going to dredge. And then as we’re dredging, we map it to make sure we’re dredging in the right spot and removing the right quantity. But as part of that mapping effort, we’re also looking at whether there is sediment accumulation in certain areas.
We expect there will probably be maintenance dredging, but our anticipation is that the dredging wouldn’t be the whole stretch of the river. So our goal is to learn more through collecting data, mapping the bottom, and figuring out where we need to maintain.
In this 2021 photo, sediment and water are pumped from the county’s dredge on the Yahara River into a basin near Babcock Park in McFarland. As sediment settles to the bottom of the reservoir, water flows back into the river.
Can you share an example of where you really saw the impact of this work?
Overall I’ve had a lot of support for the project. So whether it’s because people feel like they’re not going to be flooded, it gives them some calmness that there’s a solution that may help.
There’s also people that don’t even live on the lakes that benefit from the navigation perspective. Now they can get their boat through the river without their propeller being damaged because they’re hitting the bottom, so it provides them that navigation path.
What is the most rewarding part of this project?
The most rewarding part is seeing the growth of our staff, seeing how well they’ve been able to do the work, as well as providing that impact for the community. I think that’s the greatest part about what we’re doing — is the benefit overall that the community will have.
Is there anything you’ve learned about yourself since you started these sediment removal projects?
I think the main thing is just having patience for myself. You know, stuff takes time. And I think people in the community have learned this, too. It’s actually a lot of work to remove all that sediment: the planning, the engineering, the construction. There’s rainy days, cold days. There’s so much variability. So just understanding that things take time.
