Lapses in construction oversight of the Keystone oil pipeline and gaps in owner TC Energy's standards, policies and administrative controls were the root cause of last year's massive spill into Kansas waterways and property, said a third-party independent analysis released with redacted details. 

The report by Ohio engineering consultant RSI Pipeline Solutions was posted by the US Transportation Dept. Pipeline and Hazardous Materials Safety Administration on May 15. Canada-based TC Energy hired the consultant to investigate the leak's casue, with owner-ordered redactions reviewed by the agency that included the name of Keystone's construction contractor and pipe manufacturer.

Some 588,000 gallons of crude oil spilled from the 36-in. pipe on Dec. 7, 2022, the worst accident in Keystone pipeline history. TC Energy's cleanup operation, with as many as 800 onsite personnel, was overseen one month later by the U.S. Environmental Protection Agency under an agreement between the firm and agency

TC Energy said April 28 in its quarterly financial report that about “98% of the released volume has been recovered and cleanup is approximately 90 per cent complete.” Cleanup cost is estimated at about $480 million. The pipeline firm said it expects to remain on site until the third quarter to finish restoring the shoreline of the creek where most of the spilled oil flowed. "We continue progressing with restoration activities ... and environmental monitoring is ongoing," TC Energy said.

The 2,687-mile Keystone Pipeline System, which extends from Alberta to oil refineries in the Midwest and along the Gulf Coast and had been shut for 21 days after the rupture, opened in sections since then and continues to deliver its contracted volumes of about 585,000 barrels per day, the company said.

The pipeline agency said in March it was concerned about the risk of additional spills and ordered the reduction in pressure until it approves an increase. 

Richard Prior, president of TC Energy's liquids pipeline operations, said in April that the company is confident in pipeline reliability.

The U.S. Government Accountability Office documented 22 leaks along the Keystone pipeline between its construction in 2010 and 2020. TC Energy was required to investigation the largest four, which regulators found “were caused by issues related to the original design, manufacturing of the pipe or construction of the pipeline,” GAO said in a 2021 report.

Cracks Found in Excavated Pipe

RSI said three cracks in the pipe were found after it was excavated that were caused by fatigue and were “coincident with lack of fusion.” The pipe was lined "with a tightly adhered, high-temperature oxide scale that formed during the welding process,” the consultant said. Its report also noted that weld workmanship was compliant but was not sufficient to address the added stress. 

Lapses in construction oversight and quality control during pipe installation allowed construction techniques that “introduced a large bending stress in the pipe’s bend assembly,” the consultant said. 

Finite element analyses performed by RSI of various loading scenarios “showed loads introduced during construction in 2010 most likely overstressed the bend assembly,” said its report, which placed enough pressure on the circular pipe to bend it into an oval shape. The stress caused cracks that then grew “by pressure and temperature cycle fatigue over the operational life of the bend assembly.” Material properties of pipe components did not contribute to the incident, according to the consultant.

The report also noted that TC Energy standards, policies and administrative controls did not address the need to re-run a construction caliper tool after significant pipeline modifications. Also not addressed was the oval shape of the pipe when discovered during a 2012 caliper survey, the consultantt said.

Operating at Higher Stress

The pipeline agency had issued TC Energy a special Keystone permit in 2007 with 51 conditions for the oil line to operate at a stress level up to 80% of the steel pipe’s specified minimum yield strength. Federal regulations limit operating stress levels for hazardous liquid pipelines to 72% of minimum yield strength.

The permit requires Keystone to implement more rigorous design, inspection, testing and oversight of pipe manufacturing and pipeline construction, as well as state-of-the art leak detection systems. It also requires TC Energy to more closely inspect and monitor Keystone over its operational life than for similar pipelines operated at a lower percent of yield strength. 

The agency did not allow the energy firm to fully operate the line at the higher stress level until 2017, after the owner replaced pipe affected by industry-wide pipeline quality issues, GAO said in its 2021 report.

Based in part on its experience overseeing Keystone, the pipeline regulator increased resources to conduct inspections during construction of other pipelines and established a more formal process to document and track special permit compliance.