It’s been just over a year-and-a-half since an explosion occurred in Wheatley, Ont. that left the community reeling.
Recently, members of that community were given an update on the investigation and next steps.
The incident occurred on Aug. 26, 2021 damaging buildings in the community and leaving many injured.
“The Ontario government and Chatham-Kent did engage some external consultants and they have been assisting us to investigate the source and the pathways of the leak that caused the explosion as well as provide technical advice and guidance and information to inform mitigation,” Jennifer Barton, assistant deputy minister with the Ministry of Natural Resources and Forestry (MNRF) told attendees during the meeting in early March of this year.
Sean McFarland, senior principal with WSP Golder, shared an update on the results of the investigation and recommendations for the future. Three areas of potential environmental concern (APEC) were identified.
“Our first conclusion is the pathway for the natural gas that caused the explosion in the building was from the APEC 1 water well,” he said.
“We found there was a concrete caisson under the floor slab on the adjacent property and the gas was coming up the water well, going down through the caisson and coming out a hole in the bottom of the caisson. From there it flowed into a clay drain that was actually tied into the water well and the caisson. From there it flowed up from the drain into the basement.”
McFarland noted information was shared with the public at the September 2023 meeting and but over the last few months the team has been conducting the geochemical component of the investigation.
“The conclusion there confirmed our original opinion, that the geological source of the gas is the deep Silurian strata, particularly the A1 and A2 carbonate units of the Salina formation and possibly the Guelph formation and the interpreted conduit surface is through a deep gas well or multiple gas wells,” he explained.
“There may be other undocumented wells inside or outside of Wheatley that contributed to the natural gas in the shallow bedrock aquifer given the drilling history in the area. Additional work outside the scope of the investigation would be required to attempt to identify and locate these wells.”
McFarland provided some recommendations.
“The first recommendation is to plug any existing potential pathways for natural gas migration through the clay materials,” McFarland noted. “This would include, but not be limited to, unplugged petroleum wells and unplugged water wells should they be identified.
“We’re recommending they
be plugged so they’re not a conduit for the gas bearing bedrock up through the clay materials at surface and a potential source for explosion.”
The team also recommended to prohibit drilling and pumping of any new wells or bore holes in Wheatley that could lower groundwater levels and induce gas kick or larger scale gas emission events for as long as the gas levels remain high in the bedrock.
Prohibiting any future construction of buildings or structures over wells whether they’re petroleum wells or water wells was also recommended as it could serve as an area for gas collection that could result in an explosion.
Theresa Watson, president of T.L. Watson and Associates, prepared a technical safety report.
“What are the ongoing risks in the area?” asked Watson. “From my perspective, nearby oil and gas wells, whether they are documented or undocumented, soil and gas migration, water wells and historic buildings connected to subsurface infrastructure.”
The original source of the gas was most likely not the Tait Well, she pointed out.
“If another well is not located in close proximity and found to be the main pathway or source of the gas, finding and shutting off the pathway to the impacted area will likely not be possible,” Watson noted. “In that case permanent venting and management of the site will be required.”
In terms of recommendations, Watson suggested further testing to establish the actual venting rates and concentration.
“We’ve already done that, but I would expect that we will be redoing that test sometime in the spring to see if we have any change,” she said. “Due to the unpredictable nature of the emissions still I’m recommending that we maintain the current evacuation zone…that we remove the nail salon and the car barn buildings…and excavate to confirm or deny the existence of another gas well.”
She also recommended the town not allow any enclosed development at the site due to gas migration issues and that water well development in the area be curtailed and the withdrawals from existing wells be limited. Furthermore, she recommended the gas migration work be expanded out to the neighbouring property.
Ryan Brown, director of public works for Chatham-Kent, said the municipality continues to assist property owners impacted by the explosion.
“Were going to continue the conversations with property owners in the current evacuation zone regarding potential property acquisition,” he said. “We’ve started those conversations and we will be working with the owners to continue them.”
The MNRF is developing a comprehensive long-term action plan to look at oil and gas from a broader perspective.
“We do want to look at the situation right across the province and really start to address the challenges associated with legacy gas and oil wells as well as subsurface gas,” Barton said.
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