Nov. 30 (UPI) -- Mechanical damage from construction of a section of the Keystone pipeline in 2008 in South Dakota likely resulted in the latest release, a federal report found.
TransCanada closed down much of the 2,687-mile network in North America in mid-November after reporting a release of about 5,000 barrels of oil in rural South Dakota. The company said it recorded a drop in pressure early on the morning of Nov. 16 and triggered the shut-down process.
The federal Pipeline and Hazardous Materials Safety Administration said in a corrective action notice to TransCanada the release was likely the result of damage from when the section of the pipeline in South Dakota was originally installed.
"Preliminary information indicates the failure may have been caused by mechanical damage to the pipeline and coating associated with a weight installed on the pipeline in 2008," the report read. "Weights are placed on the pipeline in areas where water could potentially result in buoyancy concerns."
The company so far said there's been no water contamination and the release posed no immediate risk to public health. As of Sunday, that latest date for which it provided an update, the company said it's recovered 1,065 barrels of what was spilled.
The federal order calls on TransCanada to keep a small section of its Keystone pipeline between pump stations in South Dakota closed as continued operations "would be hazardous to life, property, and the environment without immediate corrective actions."
The company said Tuesday, however, that a repair and restart plan was approved by the PHMSA with no objections and Keystone resumed partial operations at reduced pressure. The government added, meanwhile, that further review resulted in an "unconfirmed lower spill estimate."
The PHMSA added that it awarded a special permit to TransCanada to operation Keystone at a pressure level that was about 80 percent of the steel pipeline's minimum yield strength, which was about 8 percent higher than the normal operating pressure for hazardous liquid pipelines. That permit, issued about 10 years ago, contained more than 50 different conditions related to safety and inspections.
About 400 barrels were released from the Keystone network last year. Federal investigators said that was from a "weld anomaly" on the pipeline and oil had been leaking from the pipeline at a rate of two drops per minute for an undetermined length of time.