Canada-based TC Energy said late on Dec. 14 that it will partially restart the Keystone pipeline that was. shut down after a Dec. 7 rupture that spilled about 14,000 barrels, or more than 588,000 gallons, of crude oil into Mill Creek in Washington County, Kan., and sprayed nearby areas following an alarm and a drop in pressure. 

The Calgary energy firm said the line, which carries about 622,000 barrels per day from Alberta to midwest and Gulf Coast U.S refiners, will open a section to a terminal in Illinois that did not leak, but a segment reaching south of the spill site remains shut.

The spill is the largest in the pipeline's history and largest for a U.S. crude oil line in nearly a decade, according to the U.S. Government Accountability Office. 

TC Energy said in a Dec. 17 statement that its worker deployment rose to 400 workers for site containment and cleanup, including those of third-party contractors whose names it declined to disclose. Its response crew was based about 20 miles north of the site in Steel City, Neb. 

About 7,000 barrels had been removed from the creek as of close of business Dec. 16, the company said, but state officials said full cleanup could take weeks. 

The U.S Environmental Protection Agency said the spill had not reached the Little Blue River or local drinking water wells, with “limited potential impacts to surrounding farmlands.”

TC Energy said it had “prepared for this event” and had a “secondary dam” and “additional resources’ ready. “The affected segment has been isolated and we have contained downstream migration of the release,” it said.

Officials from the U.S. Pipeline and Hazardous Materials Safety Administration, which said the agency is investigating the incident, approved the partial restart. But it said TC Energy had not submitted as of Dec. 14 the timeline or plan for full pipeline restart nor a root cause failure analysis. 

TC Energy said it has not determined the cause of the spill.

Vacuum trucks are removing oil from the creek, with booms set up to control oil spread. Two earthen dams have been built four miles downstream, said EPA.

Keystone transports about 14% of western Canadian crude oil exports to the U.S., one of just four major export pipelines from that area, according to Canada's Energy Regulator. A smaller spill in 2019 caused a 12-day line shutdown and an inventory backup, media reports said.

The pipeline has been operating at a higher pressure since 2017 under a special pipeline agency exemption, which TC Energy said then would allow it to save 10% on steel costs in using thinner but higher-grade steel, GAO said in its 2021 report. 

“Our response efforts will continue until we have fully remediated the site,” TC Energy said in a statement.

Story updated on Dec. 18 to reflect new cleanup details released