The Kalamazoo River is visible from Saylor's Landing west of Marshall , Mich., on Tuesday, July 10, 2012. A Canadian company’s failure to deal adequately with cracks in an oil pipeline and its slow response to a 2010 rupture in southwestern Michigan likely caused the most expensive onshore oil spill in U.S. history, the National Transportation Safety Board said Tuesday. The spill dumped about 843,000 gallons of heavy crude into the Kalamazoo River and a tributary creek, fouling more than 35 miles of waterways and wetlands. About 320 people reported symptoms from crude oil exposure. (AP Photo/The Enquirer, John Grap) NO SALES