Manitoba Hydro took nearly 2 hours to stop gas leak after pipeline hit by tractor in 2021: safety board

A pipeline rupture in Westman that leaked natural gas for almost two hours was the result of farm activity over shallow ground cover in a field that wasn't spotted by Manitoba Hydro.

That's one of several findings in a Transportation Safety Board of Canada report out Thursday that says the leak occurred on Oct. 5, 2021, after the pipeline was scraped by a tractor blade in a field in the McAuley area, near the Manitoba-Saskatchewan border.

No one was injured, but about 84,000 cubic metres of natural gas vented into the air from the Minell Pipeline, which is operated by Manitoba Hydro, over a period of one hour and 46 minutes.

Hydro's own standards aim for a response time of 60 minutes.

The Transportation Safety Board said the amount of soil covering the six-inch (15-centimetre) pipeline had gradually lessened due to agricultural activity. That wasn't noticed in Manitoba Hydro damage prevention surveys, the TSB said.

The rupture occurred near TC Energy's Moosomin, Sask., compressor station, which supplies the Minell pipeline, but board investigators said Manitoba Hydro failed to consider asking staff at the Saskatchewan compressor station to shut down the gas supply on its end.

That resulted in a slower response time, the TSB suggests.

Rules implemented in the U.S. a year ago require pipeline valves to be shut off within 30 minutes of a rupture being identified. Canada has no specific response time regulations in place, the TSB said.

Barriers to getting quick help: TSB

The pipeline was hit by a tractor operated by the owner of the land where the leak occurred, the report says.

Both the Minell Pipeline, which was acquired by Manitoba Hydro in 1999, and a TC Energy pipeline cross that person's land, which he has been aware of since he acquired the property decades ago, the safety board's report said.

After hitting the pipeline, the landowner — who didn't have reliable cellphone service at that location — radioed home to tell a family member what had happened.

Around 3:26 p.m., that family member reported the leak location to a TC Energy emergency number, then called the local volunteer fire department.

TC Energy sent a worker from the Moosomin compressor station. Firefighters also attended.

Roughly half an hour after the call, the TC Energy worker arrived and determined the ruptured line wasn't one of theirs. 

The family member then called Manitoba Hydro at about 3:54 p.m., but Hydro was already aware, after a sensor alarm went off at about 3:18 p.m., warning Hydro's gas system operator (GSO) of pressure and odour irregularities at the site, according to the report.

Hydro sent a technician from Brandon, a 145-kilometre drive away, to investigate.

In the meantime, another pressure alarm went off at a site over 60 kilometres downstream from the leak, at Hydro's gate station in Russell, Man. 

Another Hydro technician, from Russell, then travelled to McAuley and confirmed the leak. Hydro shut the entire Minell Pipeline down at 4:30 p.m.

Forty minutes after that, the technician from Brandon arrived and manually closed pipeline valves at one station in McAuley and another downstream of the leak site, which stopped the leak, the report said. There was no way to remotely shut down that section of the pipeline.

Line full inspection in 2009

Hydro is required by the Canada Energy Regulator to perform pipeline surveys every 15 years.

Before the 2021 leak, the most recent full inspection of the Minell line was in 2009, though partial surveys were done in 2018 between the TC Energy Moosomin compressor station and the McAuley gate station, according to the safety board. Those surveys didn't detect soil depth issues near the leak site.

After the incident, the Canada Energy Regulator ordered Manitoba Hydro to do a soil depth survey across the entire length of the Minell Pipeline. 

The survey found 10 spots with less than 65 centimetres (just over two feet) of soil coverage, including the site of the leak, the report says. Those spots were barricaded off by Hydro and crews notified affected landowners. 

Three of those sites have been remediated and opened back up to landowners, according to Hydro. The other seven will be this year.

The safety board said when the Minell Pipeline was built in 1960, it was required to be buried at least 61 centimetres underground. Investigators determined the blade on the tractor struck the pipeline at only 12 centimetres beneath the surface.

But for several growing seasons the landowner had been removing weeds and silt from the drainage area where the pipeline was buried.

Landowners are generally required to get permission before carrying out activities that disturb the ground, though the safety board's report notes agricultural activity that doesn't go deeper than 30 centimetres doesn't typically need authorization.

The landowner assumed he was in the clear because the weed and silt removal was something he had been doing in the area for years without Hydro telling him to stop, the report said.

The safety board also sent a letter to Hydro in early 2022 reminding the Crown corporation that operators need to keep tabs on soil cover depth over their pipelines "to ensure they are adequately protected against normal agricultural activities."

Hydro has met with landowners and "committed to taking the steps necessary to prevent such occurrences from happening in the future," a spokesperson said in a statement.

Hydro also recommends lawndowners always submit requests through its website before doing any excavation work.