Dec. 8, 2025
VIROQUA, Wis. — City officials say they are making steady, if complicated, progress on a long-running effort to control methane gas at Viroqua’s old landfill, as engineers continue to uncover more waste and expand monitoring around the site.
At the Dec. 2 Public Works Committee meeting, City Engineer Sarah Grainger walked committee members through the latest change order and field work, explaining why the city is renting specialized gas-monitoring equipment longer than planned and adding more probes around the capped dump.
The committee unanimously approved a $13,400 change order for additional rental of gas-monitoring equipment from consultant TRC, extending its use through early February. The item was listed as Change Order 5 and covers about seven months of equipment rental.
Grainger said the change arose when staff discovered the city would actually pay more if it tried to rent the gear directly instead of going through TRC, which receives a special discount from the supplier.
“In the holidays, we’ll be gathering more information,” she told the committee as she explained why the rental needed to continue. “We were going to get billed directly from (the rental company), and they’ve been delaying in doing it. And then when we finally got it all together, we realized that they give a special discount to TRC that they don’t give to us, so we actually would be paying more money. … Even with the markup is cheaper than if we were going directly.”
Garbage found beyond fence line
The larger concern is not just how the equipment is billed, but what it is finding.
Grainger said recent excavation near the landfill’s gate confirmed something TRC’s readings had suggested for months: buried waste extends beyond the fenced area that had been assumed to mark the edge of the old dump.
Using a series of test trenches, TRC aimed to understand why one monitoring point, known as “probe number two,” kept showing high gas levels just outside the fence.
“What has happened since we last met? Mike (Amstad) came out here, and he has been really bothered by what we call probe number two, because it still continues to produce a decent amount of gas and it’s just outside our fence line,” Grainger said, referring to TRC consultant Mike, the firm’s lead on the project. “So they ended up digging kind of like an L shape (trench), and then worked their way towards that probe to sort of see what they got. So here they saw a little bit of garbage closest to the property line. They kept getting more and more garbage.”
“So, long story short, we’re seeing waste that’s outside the fence,” she added, describing photos of refuse in the open trench.
Those findings prompted TRC and the city to rethink both where the landfill really ends and how gas is moving underground.
“The reason Mike wanted to do this was because he was trying to understand, if this is the edge of the garbage, where the fence is, why are we still getting such high readings there?” Grainger said. “And so obviously it’s because we need to change our perspective of where the end of the garbage is.”
New vents and more probes
To respond to the unexpected gas at the property edge, TRC installed what Grainger called a “monster vent” and several new monitoring probes near probe two.
The probes are two-inch perforated PVC pipes sunk about 15 feet into the ground, she said, encased in larger protective sleeves so crews can safely attach instruments to measure methane and other gases.
“So they ended up installing this monster vent. But the probes are what you see in this green area,” she said, describing a map on the projection screen. “So it’s actually like a two-inch PVC pipe that goes about 15 feet in the ground. It’s like perforated underground so that it can collect the gas, and then they put this casing pipe over top of it. So that’s, I think it’s about four inches. And so the probe that I’m actually testing off of is inside of that. It’s like a protective casing, essentially.”
TRC reused leftover rock and pipe from earlier landfill work to build a small subsurface venting system in that corner.
“When they dug all this up, they put some of the rock that we have left over from the project,” Grainger said. “When we did the original project, we stopped short because we were running into the road, and we just did not think we were going to get benefit out of keeping going. And so we still have a pile of rock there. We still have some pipe, and so he utilized that to do the sort of this little mini project here.”
“There’s rock there, but then he covered it up because he doesn’t want it venting to the atmosphere out there,” she said. “We’ve been both trying to vent, to suck gas out of the green area, but there’s also vents that don’t look just like that. Some of them … are like goose necks. But this one, this is how they ended up doing this one. We probably will end up connecting to that at some point and seeing if we can start pulling from there to help us not see any of that migration there.”
The city and TRC are using a mix of “passive” and “active” ventilation, she said. Some vents are designed just to let gas escape safely, while others can be connected to blowers to draw gas out of the waste and away from property lines.
“The trenches that we put in the main landfill area was mostly rock, and then we made this like pipe that went across the top of it, because methane rises, right?” she said. “So you’re supposed to be able to utilize the idea that you’re catching stuff at the top. So even those passive vents that were originally installed, those pipes don’t go all the way to the very bottom of the landfill. They are expecting the gas to rise and then get trapped underneath the cap, because there’s a clay liner on the top, and then the vent is supposed to allow for a spot for it to come out.”
Weather, equipment and what comes next
Winter has made the work harder. Grainger said crews have spent days in freezing conditions just trying to access and test the probes.
“We have been struggling for the last two days trying to keep doing testing out there, because the locks were frozen,” she said. “And then finally, we got the locks unfrozen, and then the hook part wouldn’t release, and then we got in, and then we could test. But then when we were trying to take off the couplings to put on the suction, it was frozen. We have been, it’s been two days of frustrations in the snow with this, but we’re getting there.”
Those difficulties underscore a broader shift in TRC’s recommendations. While the firm and the city initially tried to “make do” with simpler setups to save money, Grainger said winter conditions and the long-term nature of the problem mean they now need more robust, permanent equipment.
“What it really comes to is that we’ve been really trying to make due with what we can, because we don’t want to spend more money than needed, because we’ve spent a lot already,” she said. “But that’s worked well in good weather. But now, in bad weather, we need to have something a little more sophisticated, so that’s what we’re working on.”
TRC’s Mike Amstad has also been pushing to design features that will work both now and later, Grainger told the committee, so the city doesn’t have to throw away what it has already installed if regulators require more aggressive gas control in the future.
“The one thing that Mike’s been really great about is that the construction parts that he’s put in have all been intended to also have multi‑purpose,” she said. “So we were hoping for it to be passive ventilation or venting. If we need to go active ventilation, we can still use the stuff that we have in there, right? So it’s not like, ‘Oh no, we got to go to a whole another system, and we’re going to start new.’ We’d be starting with what’s in place.”
Budget, long-term monitoring and Hanson Farm tie-in
Grainger reminded the committee that the city’s original methane mitigation budget was $750,000, covering both construction — trenches, vents, rock and pipe — and consulting, including TRC’s design and monitoring work. She presented an updated spreadsheet showing what has been spent, what is committed and what remains unspent.
The city is also coordinating its landfill work with the Hanson Farm development and new utility lines nearby. Grainger said her team wants to make sure new water and sewer trenches do not unintentionally create pathways for gas to migrate.
“We do know that we’re always going to have to monitor the landfill, without a doubt,” she said. “In the Hanson farm property, we want to make sure that we mitigate any migration that’s happening. And so while we’re already digging in there, we want to make sure we’re not making a conduit to go further in. We want to cut off anything that might be in a sand layer, or any kind of trench that we’re creating, like for sanitary sewer or the water mains.”
More clarity is expected after TRC installs the remaining 17 gas probes along the east and west sides of the landfill. Those probes, required by the Wisconsin DNR, will give the city a full picture of gas levels “on all sides,” Grainger said, and help shape TRC’s next round of recommendations.
“We won’t really know any more until you get all those probes in,” Committee Chair Cyndy Hubbard said during the discussion.
“Correct,” Grainger replied. “We’ll have a better picture when we have our probes. … In the holidays, we’ll be gathering more information.”
For now, the committee has backed TRC’s approach: continue renting and using the monitoring equipment, expand the probe network and build venting systems that can be scaled up if regulators or gas levels demand it.
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