Friday, September 9, 2011

Looking behind the curtain on the SR 433 Lewis and Clark Bridge

by guest blogger Heidi Sause

The SR 433 Lewis and Clark Bridge is arguably one of the most impressive structures to stretch across the Columbia River. Built in 1929 by Joseph Strauss, the same man who engineered San Francisco’s Golden Gate Bridge, the steel behemoth towers 340 feet above the river and forms a mile-long link between Longview, Wash. and Rainier, Ore.

On a normal summer day, the gray bridge stands tall and proud as vehicles rumble across its deck and maritime traffic sails on the river below. This summer, however, crews have wrapped several portions of the steel structure in large white tarps that give drivers the sensation of traveling through a tunnel, or maybe a large circus tent. The tarps form the outer layer of containment systems that teem with dozens of workers repainting and preserving thousands of steel beams that rise above the roadway.

The structure is built out of nearly 12,000 tons of steel, and all of it is susceptible to rust. It has been 27 years since the bridge was last fully painted. The old coating is peeling away, and the underlying steel is badly rusted. If left too long, the rust will severely damage the metal and compromise the structural integrity of the bridge.

At any given time, there are between 20 and 40 men and women working on the bridge. Our contractor, Odyssey/Geronimo JV of Houston, Penn., began work last year on the third and final phase of painting work. In 2008 crews painted the Oregon approach to the bridge, and in 2010 a separate team cleaned and painted the massive piers that anchor the bridge in the river.

Odyssey/Geronimo has split their workforce into three teams to tackle the rust and recoat the bridge. The rigging crew assembles the scaffolding and tarp structures, called containment platforms. The platforms provide a work zone for the painters and help keep old paint and debris from drifting down to the river below.

Inside the sealed containment platform, the blasting crew uses high-pressure air hoses to direct a coarse, gritty substance at the steel. The abrasion strips away old paint and cleans rust from the beams. By the end of this process, the 80-year-old metal shines factory fresh, looking as it might have when it first rolled off the Pittsburgh assembly line in the late 1920s. The old paint and debris is vacuumed out of the platform and safely disposed.

The blasting team primes the exposed steel, and painting crews add an additional four coats of primer and paint to the metal. Each coat of paint has a unique purpose, but they all work to seal the metal against the elements and prevent future corrosion. The steel is still in good shape, which tells us that this project is taking place at exactly the right time. Rust hasn’t damaged the bridge beyond repair, making the painting process quicker and less costly than it would otherwise be.

Painting teams endure dizzying heights, fierce winds and blistering heat to get the job done, but in the end, it’s worth it. By stripping the bridge down to bare metal, we are restoring it from the inside out to ensure the historic structure will continue to stand strong well into the future.