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.