Updated Feb. 13 with statement from the Missouri Department of Natural Resources – TransCanada officials have located the part of the Keystone pipeline that was the source of an oil spill in St. Charles County last week. Workers are preparing to replace the section of the pipeline that leaked. The amount of oil spilled may be less than the 43 barrels the company originally reported, according to the Missouri Department of Natural Resources.

Original story from Feb. 7:

Energy company TransCanada has shut down a part of its Keystone oil pipeline to investigate a leak that occurred in St. Charles County.

A TransCanada technician discovered crude oil near the Keystone base pipeline covering an area of approximately 4,000 square feet at 7:14 a.m. Wednesday. The leak occurred in north St. Charles County on private property, just southeast of Two Branch Marina, according to the Missouri Department of Natural Resources.

TransCanada does not know the precise amount that has leaked, but estimates that it was 43 barrels. At first, it was unclear which pipeline caused the leak, said Matthew John, public-information officer for TransCanada. Another Canadian energy company, Enbridge, has a pipeline that runs parallel to the Keystone pipeline.

“Until you can excavate and see the top of the pipes, you can’t really determine which pipeline the release occurred from,” John said.

TransCanada later determined that its Keystone oil pipeline was the source of the spill. An excavation study revealed that Enbridge's Platte pipeline, which runs parallel to the Keystone pipeline, was not the source of the leak.

The company does not know how long the section — which runs from Steele City to Patoka — will be closed. Since Wednesday, workers have been vacuuming up the spill and will dig to find out the source of the leak.

“Our immediate focus is to make sure this site is contained and safe,” John said.

The spill poses no threat to waterways or endangered species, said Brad Harris, chief of the environmental emergency-response section for the Missouri Department of Natural Resources.

Credit Mapbox, OpenStreetMap A portion of TransCanada Corp's Keystone oil pipeline is shut down due to a spill that covered an area of land about 4,000 square feet in north St. Charles County near Highway C, just southeast of Two Branch Marina. The map shows approximately where the spill took place.

“We were very fortunate in the fact that there’s a natural containment the oil resides,” Harris said.

In the past, environmentalists in Missouri have protested against the Keystone pipeline’s transportation of oil from Canada’s tar sands. Area residents have complained that the low quality of steel the pipeline is made from increases the likelihood of leakage, said John Hickey, director of the Missouri Sierra Club.

“[Leaks] are one more reason on top of climate change to show that tar sands are dangerous and should not be running through our state,” Hickey said.

The Keystone base system pipeline — a separate system than the controversial Keystone XL pipeline — delivers 590,000 barrels of crude oil per day from Alberta, Canada to Cushing, Oklahoma.

Follow Eli on Twitter: @StoriesByEli

Send questions and comments about this story to feedback@stlpublicradio.org.