A portion of TransCanada Corp’s Keystone oil pipeline remained shut on Thursday for investigation of a possible leak on its right-of-way near St. Louis, Missouri, a company spokesman said. TransCanada shut the pipeline on Wednesday between Steele City, Nebraska and Patoka, Illinois and sent crews to assess the situation, spokesman Terry Cunha said in an email. The 590,000 barrels-per-day Keystone pipeline is a critical artery taking Canadian crude from northern Alberta to U.S. refineries. Two pipelines operating near the release site will be excavated on Friday to determine the source of the leak, said Darius Kirkwood, a spokesman for the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration. The agency is monitoring the response to the reported leak, he said. Canadian pipelines are already congested because […]