Erosion played role in pipeline rupture
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Manitoba Hydro says it accepts the findings of an investigation into the rupture of one of its Westman-based natural gas lines and is committed to preventing such incidents in the future.
A company spokesperson made the statement on Thursday after the Transportation Safety Board released a report on its investigation into the incident in which it concluded lack of ground cover above the pipe was a factor.
“Manitoba Hydro has already taken steps to complete a depth of cover survey for the entire Minell Pipeline and meet with affected landowners, as well as committed to taking the steps necessary to prevent such occurrences from happening in the future,” media relations officer Bruce Owen stated in an email to the Sun.
The Transportation Safety Board laid out the following findings in a press release issued Thursday, a March 2022 pipeline safety advisory letter it sent to Manitoba Hydro, and the report itself.
According to the TSB, on Oct. 5, 2021, the Minell pipeline was struck by a farm tractor blade as it scraped the ground in a field near McAuley, 110 kilometres northwest of Brandon. The tractor was pulling the blade along the bottom of a drainage ditch to ensure it remained clear.
The six-inch-diameter, steel natural gas pipeline operated by Manitoba Hydro ruptured and released 84,000 cubic metres of natural gas. The gas didn’t ignite, no evacuation was needed and no one was injured.
However, the pipeline was shut down for three days, causing a disruption of distribution that extended to Dauphin. No residential customers lost gas service, but large commercial clients were asked to cut back their operations to conserve the remaining gas in the line.
“The investigation revealed that the depth of ground cover over the pipeline at the occurrence location was insufficient to prevent the ground-scraping blade from contacting the pipeline,” the TSB found.
Over time, the removal of weeds and silt from a drainage ditch reduced the depth of cover over the pipeline, but this wasn’t identified by Manitoba Hydro’s damage prevention program. A 2009 pipeline depth of cover survey didn’t identify a problem or trigger further assessment of the area. It was estimated the tractor’s blade had penetrated the ground less than 12 centimetres when it hit the line.
The TSB also questioned Manitoba Hydro’s response to the pipeline break. The rupture happened near a TC Energy compressor station near Moosomin, Sask., that could have been used to stop the flow of gas through the line in five minutes, but Manitoba Hydro didn’t have access to it, nor did it have a formal emergency response agreement with TC Energy. As a result, gas continued to flow to the rupture for 106 minutes after a rupture was suspected, until Manitoba Hydro was able to isolate the leak.
The Minell pipeline was installed in 1965 and extends 70 kilometres from Moosomin to Russell, mostly through farmland, according to the safety advisory letter sent by the board to Manitoba Hydro.
Farming activities are allowed on land over the pipeline to a depth of less than 30 centimetres and doesn’t require authorization unless it is done at a specific location where there is a risk to the pipeline, as identified by the pipeline company.
The safety advisory letter told Manitoba Hydro operators need to be aware of the depth of cover to ensure pipelines are adequately protected against normal farming activities that don’t require explicit authorization.
More specifically, the TSB reminded Manitoba Hydro that, under the Canada Energy Regulator Onshore Pipeline Regulations, it was to maintain a pipeline damage prevention program that should include ongoing land-use monitoring to identify hazards and manage risks to the pipeline over time.
The board noted it is not its function to assign fault or liability. It suggested Manitoba Hydro review its damage prevention program to make sure the Minell pipeline is protected.
The board notes that following the rupture, the utilities company surveyed the depth of cover along the full extent of the Minell line in response to an order made by the Canada Energy Regulator. As a result, 10 sites that had less than 65 centimetres of cover were staked or barricaded. The company also provided written notice to the landowners of those sites that agriculture work, vehicle crossings and ground disturbance wouldn’t be allowed there.
The TSB also pointed to the landowner’s actions as a contributing factor. The landowner knew about the pipeline and the “click before you dig” requirement to identify underground hazards, but didn’t consider the drainage ditch scraping to be a ground disturbance that required authorization from Manitoba Hydro, the incident report states.
Manitoba Hydro took steps to prevent further incidents, the board noted, including sending a pipeline safety awareness alert to Keystone Agricultural Producers and the Association of Manitoba Municipalities, and improved tracking of its progress on fixing areas where there wasn’t sufficient ground cover.
In his statement on behalf of Manitoba Hydro, Owen also reminded individuals that they should always submit a line locate request through clickbeforeyoudig.com to avoid infrastructure.