The 10 stories we've submitted expose serious flaws in federal and state regulations that are supposed to ensure the safety of the nation's oil pipelines. These flaws are of particular concern right now, because the regulations are setting the standards for thousands of miles of new pipelines that are being built or repurposed to carry heavy crude oil from Canada's tar sands region. U.S. imports of this type of oil, which is turned into a fuel known as dilbit, are expected to quadruple in the coming decade. The core of our reporting is a three-part narrative about a 2010 pipeline accident in Michigan, “The Dilbit Disaster: Inside The Biggest Oil Spill You've Never Heard Of,” which also appeared as an e-book. In the other stories that appeared during our 15-month investigation, we applied what we learned from that disaster to the proposed pipeline projects, including the Keystone XL and the replacement of the Michigan pipeline that ruptured in 2010.