In July 2011, a TransCanada natural-gas pipeline in Wyoming exploded. The Canadian Broadcasting Company found internal company documents explaining how it happened: negligence.

“We are in trouble on the Bison project,” the pipelines’ construction manager wrote in a Sept. 18, 2010, internal email that lists problems related to welding and inspection. Construction of the project had started in August 2010.

The U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) inspected the Bison project in September 2010, and took issue with the quality-assurance of inspections, the qualifications of people working on the pipeline and the procedures used to test the coating on the pipe. …

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CBC News also obtained an all-staff internal memo issued by TransCanada CEO Russ Girling on Aug. 11, 2011, in which he acknowledged problems with an earlier phase of the existing Keystone line, and the ill-fated Bison pipeline.

“We have experienced some challenges with the startup of our Keystone and Bison pipelines which has been disappointing for both TransCanada and its customers,” he wrote.

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Publicly, the story was different.

Two months before the Bison line rupture, TransCanada’s director of pipeline integrity was quoted in an industry trade journal saying that Bison was built with “state-of-the-art” technology. “They [the pipelines] will be in place for 20 or 30 years before they need any repairs,” the director said.

An engineer sent to inspect the pipe expressed his concerns.

“I worry with the poor welding inspection that we may have a problem, but getting it done is a pretty significant problem as well,” TransCanada engineer Evan Vokes wrote in response to the Sept. 18, 2010, email from the manager. …

TransCanada had sent Vokes, the metallurgical engineer, down to Wyoming in September 2010 to help sort out problems with poor inspections on the Bison pipeline.

Vokes found what he said were examples of shoddy welding and poorly trained inspectors who were not identifying all the welding problems.

“There was a problem with everything,” Vokes told CBC News senior investigative correspondent Diana Swain in an exclusive television interview. “It seemed like every time you turned around, there was a new one.”

TransCanada is currently building a tar-sands pipeline in Texas. Last week, it shut down an existing portion of the pipeline due to possible safety issues.

We’ll know how safe the new pipeline is when the CBC scores some internal documents in a few years.