The city of West Fargo hopes to flush out the public’s preferences on cost and odor tolerance when it comes to decommissioning the city’s lagoon system.
The city has long used the 460-acre lagoon system near 12th Avenue North to store its wastewater. But every spring, the warmer weather causes the water near the bottom sludge layers to churn upward, emitting fumes of hydrogen sulfide which northerly winds can blow through the city for weeks at a time.
After years of the annual olfactory assault, many residents turned their noses up at the idea of wastewater lagoons and in 2017, the city reached an agreement with the city of Fargo's regional water treatment facility.
Wastewater began flowing to Fargo this fall. By next year, West Fargo will pump all of its wastewater to Fargo, eliminating the need to use its lagoons.
At a meeting Wednesday, Nov. 6, with city staff and commissioners, City Engineer Dustin Scott and Erik Gilbertson, a senior engineer with Moore Engineering, said there are a number of options for how to decommission — or drain and cover — the lagoons, but timing, cost and overall amount of stench the process could raise are factors.
“The first time we decommission a lagoon, it’s going to stink,” Gilberston said. “Once the phone starts ringing, the citizens might say, 'To hell with cost, we just want to get rid of the odor.' Unfortunately, the forefathers of West Fargo built the lagoons upwind of town; now we're paying the price.”
Some of the lagoons have been in use for more than 50 years, while the youngest has only been in service for about two years.
Scott said the first step of decommissioning a lagoon is to get the water out, and then the city must decide how to dry or discharge the sludge. It could be dried and dug out or some could be mixed with water and sent along to Fargo, but the current treatment plant won’t be ready to take in that much additional water until at least 2021.
The sludge may be able to be shipped or spread in agricultural treatments.
Scott said the cost of decommissioning the lagoons could land between $17 million and $30 million, depending on which options are used.
“This isn’t going to be cheap,” he said.
One of two alternatives city staff is considering would be to let the lagoons air dry and then dispose of the sludge through land application.
However, it could cost the city $21 million to $25 million, and the possibility of strong odors is high.
“The key is going to be duration of the smell — if it’s going to be a day or two or weeks,” Commissioner Mike Thorstad said.
Another alternative that would use onsite reclamation of the sludge could cost less with a $17 million to $20 million price tag, but the odor likelihood is very high.
“Where we end up is looking at the cost, since smell is hard to capture,” Scott said.
Initially, city officials said they hoped to have the lagoons decommissioned by 2024. But, officials said Wednesday, many factors need to be considered, so the timeline will remain flexible.
Scott said the city hopes to align the lagoon decommissioning with the construction of the Fargo-Moorhead diversion, which will run near the lagoons. Excess soil from the construction of the diversion could be used to fill in the lagoons.
Scott said the first cell, likely Cell 10, which is the newest, could be decommissioned starting in 2021 for about $1.5 million.
"Cell 10 would be the easiest one to do; there is basically no sludge in it," he said.
Then the city would move to the lagoons to the north, getting to the oldest lagoon cells in 2024 and 2025, which is when the odor would likely be at its worst.
"Or you could try and do the worst cells all together in one year and knock it out, but it would be the worst year of the smell," Gilbertson said.
Once the lagoons are decommissioned, about 600 acres of land may be sold for commercial or residential development. If the F-M diversion is in place, the lagoon area will come out of the flood plain, Scott said.
“This whole thing was started for two reasons: the odor and economic development,” Commissioner Eric Gjerdevig said.
Planning Director Tim Solberg said commercial land is selling for about $2 per acre, but the city must consider the money development could generate.
"This isn’t a situation where you make money on the sale of the land," he said. "You want to create an investment opportunity."
City Administrator Tina Fisk said the lagoon decommissioning project will not be assessed to residents, but the city could consider charging a small fee to sewer bills that could be taken off once the project is complete.
Scott and Gilbertson plan to continue studying alternatives for the decommission process and may present options to the City Commission in early 2020.