Spills from the Keystone pipeline, including one in South Dakota this month, have exceeded the amount predicted by its developer before the pipeline began operating, Reuters reported Monday.

According to documents reviewed by Reuters, TransCanada Corp. and a risk management company told regulators they estimated the risk of a Keystone leak of more than 50 barrels of oil was “not more than once every seven to 11 years over the entire length of the pipeline in the United States.”

In South Dakota, the firms estimated the pipeline would leak “no more than once every 41 years.”

ADVERTISEMENT

The Keystone pipeline spilled 5,000 barrels of oil in rural South Dakota earlier this month. It reported previous spills in 2011 and 2016. It began operating in 2010.

The leak came days before the Nebraska Public Service Commission approved a permit allowing a new TransCanada project, the Keystone XL pipeline, to cross the state. Regulators in the state could not factor in previous oil spills because spill prevention and cleanup is considered a federal issue, not a state one.

The Keystone XL project is still subject to legal challenges and federal permitting decisions.

As of Friday, TransCanada had recovered 44,730 gallons of oil from this month’s Keystone leak. At the time, the company said it had 170 people working on site to clean up the spill.