After an alteration of the BNSF Railway bridge (Burlington bridge) in Burlington, Iowa, was completed in 2012, the United States Coast Guard (Coast Guard) requested that we audit the sharing of costs, known as the final apportionment of cost, to determine its accuracy. Coast Guard could not provide proper documentation to support the final apportionment of cost for the Burlington bridge alteration, of which $74 million was allocated to the Coast Guard and $8 million to BNSF Railway (BNSF). Specifically, the Coast Guard did not properly document its review of the construction contractors who bid on the new bridge. In addition, the financial documentation for changes to originally planned work did not always support the cost of the work. The Coast Guard also did not have a process to evaluate and verify BNSF’s reported salvage value or expected savings in maintenance and repair costs. Based on our review of available documentation, we were unable to confirm either the Coast Guard’s or BNSF’s share of the final cost to alter the Burlington bridge. As a result, the Coast Guard cannot be certain it was appropriate to pay $74 million as the Federal share of the final cost of the bridge alteration.