Point Bonita Lighthouse Bridge
Completed in 1855, the Point Bonita Lighthouse showed the way through dangerous fog and cold as steamships entered the San Francisco Bay in search of California's gold. The lighthouse still operates today and serves as an historic attraction in Golden Gate National Recreation Area. A suspension bridge providing access to the lighthouse was constructed in 1954 after a large section of the bluff east of the lighthouse fell into the ocean. Over time, the harsh elements of the Pacific Ocean took their toll on the bridge and it was closed to the general public in 2008. Inspections called for a replacement to improve safety for lighthouse operators and reconnect visitors with the recently renovated lighthouse.
When designing the replacement bridge, HDR engineers faced several challenges. The site frequently experiences winds of more than 100 mph and is located near the seismically active San Andreas Fault. The underlying bedrock has a history of collapse, with a drop of more than 100 feet from the bridge site into the ocean. Constant salt spray creates a highly corrosive environment, necessitating unique construction materials and protective coatings. Access to the bridge is on a steep, half-mile trail that includes a narrow 6-foot by 6-foot hand-carved tunnel, so the site was not accessible with traditional construction equipment. The team had to cart construction materials to the site by hand or by all-terrain vehicles.
To address these issues, HDR designers incorporated unique materials to combat corrosion while closely replicating the historic intent of the original bridge. The new structure reuses the existing bridge foundations, thus reducing costs and minimizing impacts to adjacent historic radio tower supports. By incorporating a construction management general contractor (CMGC) process to collaborate on a constructible and cost-effective solution, the team completed the project on schedule and on budget while maintaining 24/7 U.S. Coast Guard access to the lighthouse and protecting the habitats of endangered wildlife in the area.
As beautiful as its predecessor, the new Point Bonita Bridge is safer and designed for a longer lifespan — providing renewed access to the historic lighthouse and allowing it to continue illuminating the path of modern sea vessels.
- Bicycle/Pedestrian Project of the Year, CTF Transportation Awards, California Transportation Foundation
- Alliant Build America Award, Aon Build America Awards, Associated General Contractors
- Engineering Excellence Award, Engineering Excellence Awards, American Council of Engineering Companies of Colorado
- Honor Award, Engineering Excellence Awards, American Council of Engineering Companies
- Best Project, Small Project Under $10 Million, Engineering News-Record California