Last month’s 210,000-gallon oil spill from the Keystone pipeline in South Dakota may have resulted from damage caused during construction, according to a preliminary investigation by the U.S. Dept. of Transportation’s Pipeline and Hazardous Materials Safety Administration. According to PHMSA’s order issued to Keystone owner TransCanada, weights placed on the pipeline to counter­act buoyancy issues may have caused the damage. The investigation is continuing. TransCanada has replaced the damaged pipe section and resumed operations. Bechtel provided engineering and construction-management services for the 1,082-mile pipeline, which went into service in 2008. The PHMSA said the pipe was manufactured by Berg Steel Pipe Corp., located in Panama City, Fla.