GULL LAKE, Sask. – Abandoned water wells can pose a serious threat. Just ask a cattle producer who has pulled an animal out of an improperly decommissioned well site.
However, abandoned wells can also threaten the new water source.
Rob Walcer, senior technologist with the Saskatchewan Watershed Authority, said the purpose of decommissioning wells properly is to prevent the vertical movement of water within the hole.
Otherwise, it can contaminate ground water and other wells.
As soon as a well is abandoned, the owner is responsible to fill and seal it.
Read Also
First annual Ag in Motion Junior Cattle Show kicks off with a bang
Ag in Motion 2025 had its first annual junior cattle show on July 15. The show hosted more than 20…
At a site near Gull Lake earlier this summer, Walcer told participants in a watershed tour that while the exact procedure will vary depending on the well, the principles are the same. He said it’s best to hire an experienced well contractor to make sure the decommissioning is done properly.
The first step is to remove equipment, including pumps, wiring and pipe.
The well contractor and landowner then calculate the well’s depth, diameter and water level to determine how best to seal it off. At this point, the contractor can also see if part of the well has collapsed or is blocked.
If the water level is significantly different than what was expected, there might be a problem.
The water standing in the well is then disinfected. Walcer said the water should have a chlorine concentration of 250 milligrams per litre, which is the same level used when shock chlorinating wells twice a year to control bacteria.
“That’s pretty strong,” Walcer said.
“Low level disinfection is not strong enough to kill any of the organisms.”
How much is added depends on the source of chlorine, the size of the well and the amount of water it contains.
Typical chlorine sources include 12 percent sodium hypochlorite, 70 percent granular calcium hypochlorite and 5.25 percent household bleach. However, some household bleaches don’t contain chlorine and shouldn’t be used in wells.
The watershed authority can provide a table showing how much of each chlorine source is required for different sizes of wells and water volumes.
The next step is removing the well casing, which can be difficult when the casing has been in place for a long time.
“We’re going to remove the top 11 feet of the bored well casing,” Walcer said as a contractor carefully dug around the casing.
“It isn’t practical to remove more.”
Finally, the well is filled and sealed with a bentonite product, usually chips or pellets. Bentonite used for this purpose is a soft clay product that swells to about eight times its original size when wet.
The product is weighted so that it will fall to the bottom of the well before it starts to swell.
Walcer said bentonite should also be placed about 30 centimetres beyond the edge at the top of the bore hole to ensure the seal.
Any casing that couldn’t be removed before sealing should then be taken out and the site capped with clean clay.
Large diameter or bored wells, because of their size, require a slightly different procedure. These wells are usually 46 to 122 cm across.
In this case, a layer of bentonite is placed at the bottom of the well, followed by clean sand or gravel and then a seal of another layer of bentonite.
Small diameter or drilled wells are usually 10 to 20 cm wide and are decommissioned using a grout seal applied from the bottom up.
All wells should be capped with clean clay and mounded to prevent water from pooling at the top.
Walcer said employees of the watershed authority or Prairie Farm Rehabilitation Administration are available to help.
“We can provide technical assistance on how best to seal off a bore hole.”
The agencies also offer the “cheapest and most comprehensive” water analysis for operating wells, he added.
“We come out and look at the well and see if there’s anything impacting water quality.”
He reminded well owners to take water samples twice a year and test them for bacteria and nitrates. He advised not to use slow dissolving “pool pucks” normally used in swimming pools because they will wreck pumps and screens.
