Burlington Northern Railroad Bridge 5.1 - Rebuilding As Vertical-lift Bridge

Rebuilding As Vertical-lift Bridge

The center swing span was replaced by a vertical-lift span and towers in a two-year project completed in 1989, funded primarily by a federal grant. Prior to this change, numerous ships had struck the bridge over the years, the worst incident being the 1978 one described above, and the bridge's center pier ultimately was deemed an impediment to river navigation. That assessment was made by the U.S. Coast Guard, and it led to Congressional approval of a $38 million grant to pay for the work. Conversion to a vertical lift permitted the central pivot pier to be removed, greatly widening the navigation channel. In addition to increasing safety, the wider clearance would allow larger ships to reach the Port of Portland's then-new (1978) dry dock facility for ship repair and rebuilding at Swan Island, and Port officials cited both of these benefits in their support of the planned change. After design and engineering were completed, a $28 million contract was awarded in May 1987 to Portland-based Riedel International Inc. to actually carry out the work. The Coast Guard financed most of the cost of the conversion, but Burlington Northern paid about 3 percent of the cost.

In order to minimize disruption to both river traffic and rail traffic, the project was carefully coordinated to allow the actual change to be made over just 72 hours. This work began on August 8, 1989, with removal of the 81-year-old swing-span section, and was completed on August 11. The now-disused pivot pier was removed by dynamite blasting three months later, after the fall fish run, and with that final step the navigation channel was widened from 230 feet (70 m) to 497 feet (151 m).

The 516-foot (157 m) long lift span is one of the longest vertical-lift spans in the world and is also the fourth highest in the world. When fully raised, it provides vertical clearance of 200 feet (61 m) at low water. The new lift span weighs 7,900,000 pounds (3,600,000 kg). It is made of weathering steel, which is designed to rust naturally and thus turn a reddish brown. However, the remainder of the bridge, the fixed spans dating from 1908, are painted silver. This has given the rebuilt structure two distinct colors, and the unusual combination has been called unattractive by some.