The Trans Alaska Pipeline System, one of the largest oil delivery systems in the world, stretches from Prudhoe Bay, almost directly south to Valdez. The Valdez port is the northernmost ice-free port in North America, lying just across the Prince William Sound from Seward.
The pipeline system has been in operation for almost 30 years, moving an average of 800,000 barrels of crude per day. Keeping the pipeline clean, internally, calls for a pig in the pipe. This device is used to remove a wax buildup. Today, the oil is heated and the wax problem is less severe, but the modern version of the pig is still in service to clean and inspect for corrosion, a critical issue on the pipeline.