A gas pipeline ruptured by flood-driven debris continued to leak sour gas Thursday evening as a record-setting deluge in southern Alberta prevented workers from shutting it off.
The Calgary and Canmore regions are undergoing the worst flood in decades. With that in mind, crews from Legacy Oil and Gas were going to shut off a Turner Valley well site Thursday morning when they found the leak, says CFO Matt Janisch.
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A tree uprooted and carried by high waters hit the pipeline, Janisch said – “just sort of jammed it, and we don’t know if it tore a hole or just pulled it off a connection.”
But the flooding’s so bad – swift currents more than waist deep, Janisch said – it’s impossible for staff to shut off the pipe until the water recedes.
“There still is a small amount of flow coming from the line – we don’t have an exact number – and we will get somebody in there … to shut off that well as soon as it’s safe to do so,” Janisch said.
“There’s still a lot of water and it’s moving very quickly and there’s a lot of debris, so we’re erring on the side of safety.”
Legacy doesn’t yet know how much has leaked. “We don’t have the exact number, but it’s a very low rate,” Janisch said. He thinks water has gotten inside the pipeline to slow the flow further.
In a news release Thursday evening, the Alberta Energy Regular said on site air monitoring has confirmed that, to this point, sour gas levels have not posed a threat to public safety; however, some odours may be present.
This sour gas, about 1% hydrogen sulfide, is colourless, smells like rotten eggs and is highly toxic. According to the Alberta government, sour gas makes up about a third of all the gas the province produces. Its sulphur is extracted and used for everything from fertilizer to pharmaceuticals.
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With dozens of Turner Valley residents already on evacuation orders because of the flooding, more were evacuated as a result of the sour gas spill.
But Janisch insists no one’s at risk, even as the pipeline continues to leak: There are no residents living within the site’s 100-metre emergency zone, he said.
“I hope people recognize that we were being very proactive … and really put the residents in the safest position they could be.”
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The Alberta Energy Regulator has staff on-site, said spokesperson Cara Tobin. She said there’s no “easy answer” when it comes to what makes a sour gas spill dangerous.
“It depends how close you are, it depends on wind, it depends on length of exposure,” she said. “Any amount is dangerous. … And that’s why the town took precautionary measures to evacuate and shelter in place.”
This map shows the number of releases from sour gas pipelines in Alberta between 1975 and 2012. Each hexagon has an area of approximately 74 square kilometres.
The Turner Valley area has historically been a hot spot for leaks from sour gas pipelines. Check them all out in the table below:
Graphics by Leslie Young
Source: Alberta Energy Regulator