How We Respond

It started at 2:21 p.m. on April 3, 2018 with a phone call from Enbridge’s Leak Detection Team to Control Center Operations in Edmonton, Alberta, the nerve center of the company’s network of crude oil pipelines stretching across North America.

They weren’t calling about a leak. Rather, the team was informing the Control Center that there was a chance that two days before, on April 1, something had contacted our Line 5 pipeline in the busy Straits of Mackinac, where other submarine utilities also crossed the waterway. The pipeline was operating within normal pressures and flow rates, with no abnormal indications, but a local power company was investigating what appeared to be anchor damage to one of its underwater electrical cables nearby.

“The Great Lakes Region had become aware of the issues with the nearby electrical cables, and they reached out to our Leak Detection team, which they knew was running a pilot test of some new hydrophone technology that listened to the pipes for the acoustic signature of anchor strikes,” says Maury Porter, Manager of Enbridge’s Pipeline Control Technical Services Group in the Control Center. “The leak detection team called us in the Control Centre right away and told us what they were looking at. At that point we were still running normally, but as soon we learned that the power company was investigating damaged cables, and that the leak detection team thought their pilot system might have detected the sound of an impact on our pipeline, we shut down and began our due diligence to make sure the pipeline was okay.”

By 2:30, less than 10 minutes after the call had come in, operators had shut down Line 5 and begun the work to assess its integrity and confirm that it was fit for duty.

“We spent the day doing system integrity checks. We isolated the pipeline and we looked to see if our pressures were holding the way we expected them to. That looked good. Our leak detection models were showing no abnormalities, so that was good. And we had crews in the field, actually looking at the Straits,” Maury says. “We were confident that the line was intact and that there were no integrity concerns.”

But later in the day the Leak Detection team came back with more information. They were now more confident that the suspect acoustic signature the hydrophones had picked up did, in fact, sound like an anchor strike. And, says Maury, “we learned that there had actually been a ship in the channel, above the line, at the time that the hydrophones picked up the sound.”

Faced with conflicting information – on the one hand the pipeline was holding pressure and showed no signs of a leak, and on the other there was mounting evidence that the line had been struck by an anchor – the control center operators did what they are trained to do and kept the line shut down until they could confirm that it was safe to restart.

“Everything was pointing to the pipe being fine, but we still wanted more confirmation from further analysis or another tool that would give us even more confidence,” Maury said.

While shut down overnight, the pipeline continued to hold pressure and behave as expected, so on the afternoon of April 4 local teams ran a gauge tool through the lines, which confirmed that the pipelines had not been seriously dented.

“We were confident that the system was intact,” Maury says.  In the end, he said, Enbridge kept the line shut down for more than 24 hours as the company undertook all the steps necessary to validate the integrity of the system.

Over the coming weeks, Enbridge would send divers and remotely operated vehicles down below the waves to assess the damage from the outside. Crews also ran a smart ball through the lines to listen for small leaks, as well as in line inspection tools to assess the health of the pipeline from the inside. Through this work Enbridge identified three dents in the twin 20-inch diameter pipelines. The dents in the nearly inch-thick steel wall of the pipelines were several across and less than an inch deep.

Maury credits Enbridge’s focus on safety as the key driver in the response by everyone involved.

“The continued focus on communication and safety really drove to a true understanding of what had happened and what the condition of the pipe was,” he says. “It showed the benefit of making sure that everyone is communicating and all the information is out on the table to allow for effective decision making, ensuring you’re doing the right thing and avoiding confirmation bias.”