Tuesday Sep 22 2009
By: Gus Thomson Journal Staff Writer
Local span similar to Minnesota structure that collapsed two years ago
The towering Foresthill Bridge is due for a $70-million facelift this spring that will not only toughen its support structure but renew some of the span’s sparkle. And while Placer County owns the 36-year-old bridge, Public Works Director Ken Grehm said Monday that federal and state bridge safety and road funds should take care of most of the costs. The bridge, painted a distinctive pea-green hue, was placed on a state list for a mandatory seismic retrofit by Caltrans 10 years ago. The county is now poised to move ahead with one of the most expensive public works projects the Auburn-area has experienced. The bridge itself cost $13 million to build. Plans are to retain the appearance of the bridge with a similar color of paint while modifying bearings that support the structure to withstand a major earthquake. The bolted deck truss bridge is similar to the I-35W span in Minneapolis, Minn. that collapsed two years ago, killing 13 people. Grehm said the Foresthill bridge is structurally sound but required to have the support system to withstand a serious earthquake and remain standing. That would mean a reading of 6.0 on the Richter scale. The cost of the project is high because of the need to protect the North Fork of the American River canyon below from falling paint when it’s sand-blasted, he said. The bridge’s first and only paint job in the early 1970s involved lead-based products. “The painting is so expensive mainly because we don’t want to allow anything getting into the American River canyon,” Grehm said. “We’ve painstakingly put in a lot of requirements to ensure the environment is protected.” Full encapsulation of all or part of the bridge being sandblasted is likely to occur, with a tent-like structure keeping any debris from floating away. But Grehm said the painting contractor would be responsible for the type of cloaking apparatus to be used. The project will also see the middle of the bridge filled in with a new concrete and steel surface that could eventually turn into a third lane or passing lane. The bridge currently has two, 20-foot wide lanes, with an 18-foot drop-off between them. The extra room in the middle will allow traffic to continue to flow over the bridge between Auburn and the Foresthill Divide when the 18-month construction project is taking place, Grehm said. The cost of a new coat of green paint is coming in at an estimated $27 million. The seismic stabilization work is anticipated to cost $43 million. Railing along the side of the bridge will be replaced with a higher barrier. Minimum standards are now 54 inches or taller. The county Board of Supervisors will be asked today to approve an environmental report on the project. Grehm said the project is 88.5-percent funded through a federal bridge program, with state road funds providing an 11.47 percent match for the seismic retrofit. County road funds from a state bond issue would provide the 11.47 percent local match for work not directly related to the seismic retrofit.