Massive pipeline spill caused by crack created during installation, third

TC Energy workers at the site of a pipeline spill near Washington, Kansas, just a few miles south of the Nebraska border

A third-party review of a pipeline spill that released 500,000 gallons of crude oil onto Kansas farmland and a nearby stream was caused by a crack in the metal pipe that eventually ruptured under pressure.

That was the conclusion of a third-party review that was ordered by a federal pipeline safety agency to investigate the December failure of the 36-inch Keystone pipeline, just south of the Nebraska border near Washington, Kansas.

It was the largest oil pipeline spill in the U.S. in nine years.

The "Root Cause Failure Analysis" for the so-called "Milepost 14 incident" reached the same conclusion as an independent analysis of the metal pipeline released in February.

"The primary cause of the rupture was a progressive fatigue crack that originated at a girth weld connecting a manufactured elbow fitting to the pipe constructed across Mill Creek (in Kansas)," the operator of the pipeline, TC Energy, said in a press release Friday.

The company said that during construction of this segment of the Keystone pipeline, which as completed in 2011, "inadvertent bending stresses sufficient to initiate a crack" occurred on the elbow fitting.

Over time, and under the high pressure needed to push the oil down the pipeline, the crack worsened, eventually resulting in the leak.

The pipeline, which carries tar sands oil from Canada to refineries on the U.S. Gulf Coast, was operating at a pressure of 1,153 pounds per square gauge at the time of the Dec. 7 rupture, according to the federal Pipeline and Hazardous Materials Safety Administration.

Since 2009, the Keystone pipeline has experienced three failures on similar girth welds, according to PHMSA.

In March, the agency ordered TC Energy to reduce the operating pressure to 923 ppsg on the segment of the Keystone pipeline from Steele City, Neb., to Cushing, Okla., due to a "repetitious pattern of failures related to the original design, manufacture, and construction."

On Friday, TC Energy, in a press release, said it had recovered 98% of the released product and cleaned up 90% of the shoreline of Mill Creek, where the failure occurred. Previously, the company has estimated its cost of responding and cleaning up the leak at $480 million.

Thousands of cubic yards of oil-soaked soil and other materials removed from the spill site were trucked to a landfill just outside Omaha.

TC Energy said that in response to the failure analysis, it plans to:

The company said the latest review confirmed that the welding workmanship on the pipeline was "compliant with applicable codes and standards."

A lobbyist with the Sierra Club of Kansas, however, said the latest report just reaffirms that there were flaws in original design, material and installation of the Keystone pipeline that make more oil spills inevitable.

"This shouldn't give us any relief or assurance," said Zack Pistora of the Sierra Club. "This only reaffirms that it's only a matter of time before another weld fails or a design flaw causes another disaster."

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