Building Point Bonita Lighthouse Pedestrian Bridge
Flatiron replaced the historic Point Bonita Lighthouse Suspension Pedestrian Bridge in the Golden Gate National Recreation Area. The lighthouse, moved to its current location in 1877, was previously accessible via a suspension bridge built in 1954 designed as a model of the nearby Golden Gate Bridge. Despite two major renovations, half a century of corrosive salt air took its toll. Flatiron constructed a near-identical replica of the existing bridge. The new structure is a two-hinged suspension bridge with asymmetrical straight backstays. It has a 156 foot main span with a 55 foot approach span on the west side and a 33 foot approach span on the east side.
The bridge is located on a crumbling precipice 124 feet above the crashing waves of San Francisco Bay. Access to the site of this small but uniquely challenging project is very restricted. The only land access is along a steep, half-mile long trail and a hand-carved 118-foot access tunnel through hard rock, only about six feet tall and four feet wide. The tunnel ends near a sheer drop, a short distance from where the footbridge begins.
Special efforts were made to help the new bridge meet its expected 50-year lifespan. The deck and towers are constructed from a dense exotic hardwood, imported from the African country of Cameroon because of its ability to withstand the constant saltwater spray. Crews drilled holes in the side of the cliff and reinforced them with support rods and shotcrete in an attempt to prevent further erosion.
The bridge was completed in April 2012 and the lighthouse, a popular tourist attraction, was re-opened to an enthusiastic public. More than 2,000 people visited the lighthouse on the first weekend the bridge reopened.
Suspension bridge with 156-foot main span
Limited access to project site via hand-carved 118-foot access tunnel
Located on ocean cliff 124 feet above San Francisco Bay
Rock stabilization work