Decommissioning the Right Way

Published On: March 20, 2023By Categories: Features, Groundwater Quality

Doing it correctly protects the aquifer from potential contamination.

By William Wagner

Mantyla Well Drilling Inc. in Lakeland, Minnesota, has learned over the years how to efficiently seal decommissioned wells. Photo courtesy Richard Thron, MGWC, NGWAF, president of Mantyla Well Drilling.

The landscape is dotted with decommissioned wells that haven’t been sealed properly—or sealed at all, for that matter.

In his many decades in the business, Richard Thron, MGWC, NGWAF, has seen all sorts of peculiar evidence of poorly decommissioned wells.

“We’ve found snakes, fence posts in wells,” says Thron, president of Mantyla Well Drilling Inc. in Lakeland, Minnesota. “I’ve got a whole wall behind me with little toys and rocks and things that we have fished out of wells. Beer cans—you name it. Wherever your mind could wander to that would fit into the diameter of a well, we have found it.”

Sometimes it’s an ominous sign. The consequences of not decommissioning a well the right way can be catastrophic.

“The importance of sealing the well is that it’s a direct conduit from surface to aquifer for anything and everything to get down there and contaminate an aquifer,” says Thron who served as president of the National Ground Water Association in 2015 and presented the “Water Well Decommissioning/ Sealing” workshop at Groundwater Week 2022.

“The well could be near a gas station. Or maybe there are fertilizers nearby. We had one well that was at a building, and the building’s use changed from manufacturing to fertilizer storage. There were palates of fertilizer on top of a steel plate of a 10-inch well. It was almost the same depth as the city well half a mile away. So you can see the importance of sealing those boreholes to eliminate the conduit.”

Or consider this nightmare scenario: “We had another building that had been a repair shop. In the development of that area for a shopping center, they put an oil change facility on that [site]. They kept the slab. There was a hole in the floor [that was an old well borehole], and they decided to pour waste oil down there. The employees thought that was where they were supposed to pour the waste oil.”

It was a recipe for contaminating an aquifer, again underscoring the importance of properly sealing a well.

There are several measures that can be taken to ensure a decommissioned well won’t become a problem in the future. Those measures differ from site to site depending on a number of factors, such as the size of the well, its design, its location, and the pump system that was installed.

But here are some general rules to follow.

Leave It to the Pros

Excavation may be required when sealing a decommissioned well, so locating underground utilities is essential before digging.

This seems obvious, but all too often people don’t call in professionals to seal a well. They attempt to do it themselves, sometimes even using flimsy materials such as rags or newspapers to plug the boreholes.

“Don’t try to do it yourself,” Thron warns. “The harm you can create for your body and the neighboring wells and the environment in its entirety [is too great]. It’s a fine line—you can help or certainly destroy. If you destroy that aquifer, it may not be able to be cleaned out, so it will be forever lost. And some areas only have one or two aquifers.”

To ensure the job is done correctly, states don’t consider a well to be officially decommissioned unless it has been sealed by a licensed professional in accordance with the code that has been established.

“As a homeowner, you have to call a licensed professional to make it legal,” Thron says. “You have to get the proper legal forms filled out and filed with the state. That will take your liability for any spillage that could get into that well. Also, kids throw stuff in there, or someone could fall into an open hole. The deal is that you do have a responsibility for the future of our water quality when you have a private well.”

There are several measures that can be taken to ensure a decommissioned well won’t become a problem in the future.

In other words, make sure that responsibility is passed on to the licensed professional. Or as the Wisconsin Department of Natural Resources, Bureau of Drinking Water and Groundwater puts it: “These contractors are familiar with correct filling and sealing materials and procedures, are knowledgeable about wells, and have access to the necessary equipment.”

Clear Out the Well

After determining the condition of the well, the contractor will start by removing the pump, piping, and other materials from the well.

Install a Grout Pipe and Fill the Well

Once the well is cleared out, a grout pipe will need to be temporarily installed in the borehole to fill the well from the bottom up with neat cement. The exact mix of cement will vary, depending on the well. For the optimal seal, the pipe should extend at least as far as the first impermeable sediment layer.

The customer looks on as Thron’s company seals the well. Photos courtesy Thron.

Filling the well is a key step because, as the Wisconsin Department of Natural Resources, Bureau of Drinking Water and Groundwater says: “An improperly filled and sealed well can be as much a threat to groundwater quality as an open well.”

Fashion a Berm

A neat-cement berm around the top of the borehole will ensure that surface water doesn’t gather around the top of the well and create small openings.

Keep Your Documentation

After the job has been completed, the well owner should hang on to the paperwork. Says Thron:

“Documentation [for the homeowner] is of upmost importance. File those papers in a safe place. Let’s say your greatgrandpa lived there, and you have no clue there’s a well there. And then the property comes up for sale and the realtor asks if there was a well on the property. You wind up saying, ‘I don’t know.’ The search starts from there.”

To make that potential search easier, the contractor must also keep thorough records of work that has been done.

“Back in the 1970s or ’80s, my dad put notes on the billing that said we had sealed the well. Even though the code was not yet in effect, or today’s required forms, this billing showed that we had sealed and replaced that well.”

If you’re still not convinced about the importance of properly decommissioning a water well, here’s one final cautionary tale from Thron:

“There was a facility in the town next to us. The guy had a machine shop, and the fluids he poured on the ground went down and got in the aquifer. Now half the township is contaminated. He’s dead and gone now, but the family took a big hit, and it put them out of business. The liability was tremendous on that.”

Learn More on Properly Decommissioning a Water Well
Marvin F. Glotfelty, RG, recently covered this topic in both his column, “The Art of Water Wells,” and in a NGWA: Industry Connected video.
Click here to read more from Thron in the Water Well Journal Q&A where he discusses sealing wells contaminated by PFAS (per- and polyfluoroalkyl substances) in his home state of Minnesota.

William Wagner is an award-wining writer, editor, and project manager for Wagner Communications. He has written for magazines, newspapers, books, and websites. He lives in the Chicago area, and can be reached at

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