TransCanada's existing Keystone pipeline has already leaked a significant amount of oil three times in less than seven years. That's a much higher rate than the company predicted in its risk assessments provided to regulators, Reuters reported.

Since the 2,147-mile pipeline began operating in 2010, it has gushed 5,000-barrels just this month in Marshall County, South Dakota, and about 400 barrels each in Hutchinson County, South Dakota in 2016 and in Sargent County, North Dakota in 2011.

However, TransCanada's spill risk assessment estimated that the chance of a leak of more than 50 barrels to be “not more than once every seven to 11 years over the entire length of the pipeline in the United States,"

And in South Dakota, where the line has leaked twice, the estimate was for a “spill no more than once every 41 years."

The spill risk analysis was conducted by international risk management company DNV GL, which did not respond to Reuters' request for comment.

TransCanada could lose its permit to operate the Keystone in South Dakota if an investigation into this month's massive leak determines that the pipeline operator violated its license. Conditions include construction standards and environmental requirements.

“They testified that this is going to be a state-of-the-art pipeline," South Dakota Public Utilities Commission member Gary Hanson told Reuters. “We want to know the pipeline is going to operate in a fashion that is safe and reliable. So far it's not going well."

Nebraska regulators approved an alternative route for the Keystone's controversial sister project, the Keystone XL (KXL) Pipeline, just days after the spill in South Dakota.

President Donald Trump pushed the KXL forward in March through an executive order, overturning President Obama's rejection of the project.

As it happens, TransCanada's spill risk estimate for the KXL is also very low—2.2 leaks per decade with half of those at volumes of 3 barrels or less. Spills more than 1,000 barrels would occur at a rate of once per century, it estimated.

Meanwhile, cleanup efforts for the Nov. 16 spill are underway. TransCanada announced Friday that it has recovered more than 44,000 gallons of oil so far.

“Air quality monitoring continues regularly without concern and there have been no water issues or suspected risks to water wells. As a safety precaution, TransCanada sampled one residential water well yesterday at a location about 1.5 miles from the site to alleviate any concerns—all test results were normal," the company said.

But in a setback for the pipeline operator, a federal judge on Wednesday allowed a key lawsuit against the KXL's permit to move forward, The Hill reported. U.S. District Judge Brian Morris rejected a request from the Trump administration and KXL developers to throw out the lawsuit.