July 8, 2025
VIROQUA, Wis. – Earlier this month, the Viroqua City Council gave City Engineer Sarah Grainger the go ahead to start phase one of a remediation project the city is being ordered to undertake by the DNR to capture methane gas leaking from the old city landfill.
Last month, Grainger informed the Council they had discovered the old city landfill, that was closed in the 1990s, was leaking higher than acceptable amounts of methane gas. The City received notice from the Wisconsin Department of Natural Resources (DNR) on May 27 that the old city landfill is not in compliance with closure requirements because of high levels of methane gas discovered around the perimeter of the site. The DNR required the city to get a plan in place immediately to address the issue, and because of that, they Council gave Grainger permission to waive the usual bidding process and work with a contractor to develop a plan and cost projections.
Grainger presented some of those plans and estimates to the Council at their July 1 meeting. Grainger said she has been working with Mike Amstad with TRC Companies and Badger Environmental to work on the plan.
At last months meeting Amstad said their investigation up to that point indicated the vents that were installed on the site when it was closed are not working. Because those vents are not working the gas has found a path through layer of sand that it is following and venting around the outside of the site. Amstad’s recommendation to mitigate the gas is to install a passive venting system. That system would essentially involve digging a trench around the north and east side of the site that is filled with porous rock and a pipe that will collect the gas and allow it to vent up into the atmosphere, and not out the sides.
Grainger said phase one of the plan is estimated to cost around $230,000. Grainger went on to say the contract for that work includes two scenarios that depend on excavation depth requirements. The higher cost for deeper excavation is due to safety complications when digging beyond the 10-foot trench box capacity, which may require wider excavation areas to safely handle the landfill waste. The city received some cost relief when Vernon County agreed to accept the excavated waste material, reducing disposal costs by approximately $15,000 from the original estimate. The DNR requires the waste to be disposed of at an approved landfill rather than on-site.
Grainger said other factors could impact the overall cost to do the work including:
When the gas monitoring probes were drilled, they encountered waste materials (wood chips, plastic, and tin cans) outside the originally mapped landfill boundaries. This suggests the actual extent and depth of buried waste may be different than expected.
The trench box equipment is limited to about 10 feet in depth. Once excavation needs to go deeper, contractors face significant safety complications that require wider excavation areas to operate safely around the landfill waste.
Geological factors – the depth required depends on where the gas migration is occurring underground, which won’t be fully known until excavation begins and the actual conditions are revealed. The consultant emphasized that quantities in this construction project are “a lot more fluid” than typical projects because of these unknowns. They won’t know the exact requirements until they start digging and can assess the actual conditions encountered.
DNR has given permission for the implementation of phase one to be completed by July 30. The project is expected to take approximately one week, and it will focus on the area closest to the church where the gas was originally detected. The team will do continuous monitoring to assess the effectiveness of this first phase before proceeding with the rest of the project.
Grainger originally gave a ballpark estimate for the entire project at around $750,000, and that number looks like it may be accurate based on estimates for phase one of the three phases. Grainger said more will be known after phase one work is done.
Add comment