A proposed legal settlement with the US government would require the Keystone pipeline system’s operator to pay a $26.9m civil penalty over a large oil spill in Kansas in December 2022 and spend about $40m more to prevent future accidents.

The agreement would resolve allegations from the US Environmental Protection Agency (EPA) and Kansas that South Bow, based in Canada, violated US and state clean water laws. The rupture dumped nearly 13,000 barrels of heavy crude oil into a creek running through a rural pasture in Washington county, Kansas, about 150 miles (241km) north-west of Kansas City.

The accident was the largest onshore crude pipeline spill in the US in nine years and surpassed all 22 previous ones on the same pipeline system combined, according to a 2021 report from the US Government Accountability Office. The total amount of oil spilled would have nearly filled an Olympic-sized swimming pool.