Before dawn on a recent day in the port of Seattle, dense autumn fog hugged Puget Sound and ship-to-shore container cranes hovered over the docks like industrial sentinels. Under the dim glimmer of orange floodlights, the crew of the tugboat Millennium Falcon fired up her engines for a long day of towing oil barges and refueling a variety of large vessels, like container ships.The first thing to know about barges is that they don’t move themselves. They are propelled and guided by tugs like the Falcon, which is owned by Centerline Logistics, one of the largest U.S. transporters of marine petroleum. Such companies may not be household names, but the nation’s energy supply c …
