The Keystone pipeline had to be shut down after crews discovered a leak at their Amherst, South Dakota site about 6 a.m. Thursday morning.

Approximately 5,000 barrels, or 210,000 gallons of oil was leaked, according to a statement from TransCanada. The pipeline’s spill is the largest to date in South Dakota, KTVQ News reported.

Billionaire Democratic donor Tom Steyer, an avowed environmentalist who is on a multi-million dollar mission to get President Trump impeached, added the pipeline leak to his list of impeachable offenses Thursday.

“It’s up to all of us to stop Trump, not just from impeachable offenses, but decisions, like reviving the Keystone XL pipeline, that put Americans directly in harm’s way,” he said in response to the pipeline leak.

Below is a portion of the press release which TransCanada posted on their website announcing the leak on Thursday:

AMHERST, SOUTH DAKOTA–(Marketwired – Nov. 16, 2017) – News Release – TransCanada (TSX:TRP) (NYSE:TRP) crews safely shut down its Keystone pipeline at approximately 6 a.m. CST (5 a.m. MST) after a drop in pressure was detected in its operating system resulting from an oil leak that is under investigation. The estimated volume of the leak is approximately 5,000 barrels. The section of pipe along a right-of-way approximately 35 miles (56 kilometres) south of the Ludden pump station in Marshall County, South Dakota was completely isolated within 15 minutes and emergency response procedures were activated.

Crews, including TransCanada specialists from emergency management, engineering, environmental management and safety as well as contracted, nationally recognized experts are assessing the situation. TransCanada is providing State and Federal regulators, including the Pipelines and Hazardous Materials Safety Administration (PHMSA) and the National Response Center (NRC), with accurate and confirmed information on an ongoing basis.

TransCanada appreciates the collaborative support of local officials, emergency response personnel and commissioners in Marshall County, as well as the landowner who has given permission to access land for assessment, identification and clean-up activities.