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Flatiron Receives Alliant Build America Award for the Point Bonita Lighthouse Pedestrian Bridge

Flatiron constructed the Point Bonita Lighthouse Pedestrian Bridge which hovers 124 feet above the San Francisco Bay

Flatiron constructed the Point Bonita Lighthouse Pedestrian Bridge which hovers 124 feet above the San Francisco Bay

Outside-the-Box Thinking Lands Flatiron an Alliant Build America Award

In a spot just north of San Francisco stands the Point Bonita Lighthouse, a fixture which has guided ships through the Golden Gate, the strait that connects the San Francisco Bay to the Pacific Ocean, for more than 150 years. There’s only one way to access the lighthouse: a suspension bridge that hovers 124 feet above the San Francisco Bay. Years of corrosive salt air have taken its toll on the span, and in 2011, Flatiron Construction Corp., an AGC of California member, accepted the task of constructing a near-identical replica. Outside-the-box thinking helped Flatiron overcome challenges and implement creative solutions, contributing to the company receiving a 2013 Alliant Build America award in the category of Highway & Transportation Under $10 Million.

Think your commute is rough? Getting to this jobsite each day meant crews maneuvered through a narrow, half-mile walking trail that stretched through a 6-ft-tall, 4-ft-wide, hand-dug tunnel. “All removed and new material had to be transported along this route, including concrete for bridge anchor modifications,” says Joel Dodd, a Flatiron project field coordinator. Initially plans called for helicopters to transport equipment and supplies, but Flatiron crafted a better idea. “We devised a system using ATVs [all-terrain vehicles], modified trailers and an old-school construction approach,” says Dodd, “that eliminated the need for a helicopter” (and the expensive invoice that would have accompanied it).

Such limited access, however, meant the bridge lumber, a heavy hardwood from Cameroon, chosen for its ability to withstand wet conditions, had to be transported in small batches and raised by hand, since larger equipment could not fit through the tunnel.  New concrete arrived in 50-gallon drums and crews removed existing concrete with only chipping guns. Workers rolled 1,780 pounds of cable reels down the footpath and pulled them over the gap to the bridge by hand.

Operators of the lighthouse, the U.S. Coast Guard, required 24/7 access to the beacon during the construction process, and power could not be interrupted.  “It was very important to … maintain safe access to the signal for maintenance and repair,” says Dodd. Crews created a temporary structure and installed new cables around the old span so it could be raised and lowered as needed to provide access. It served as a tie-off fall protection system. During construction, every walk across the 156-ft span meant clipping into a safety harness. “The members of the Coast Guard received specific fall training protection from Flatiron,” says Dodd. The team’s focus on safety led to no recordable incidents or lost-time accidents on the project.

Throughout construction, the project site remained opened to visitors on the weekends, enabling tourists to see the bridge’s progress. The construction team coordinated closely with the National Park Service (NPS) to ensure the safety of the public.

Environmental hazards included lead paint on the old bridge, as well as contaminated soil on the site. Crews received special training on removing hazardous material to guarantee safety, as well as compliance.

The lighthouse and pedestrian bridge rest within the largest urban national park in the country (the Golden Gate National Recreation Area) and therefore call many different types of wildlife neighbors. That ATV idea earlier? Not only did that transport equipment, it minimized the impact on the creatures great and small in the area.

“The elimination of the need for helicopters was of great relief to the NPS as the site was the pupping location for California Harbor seals, a nearby bird sanctuary and butterfly  habitats,” says Dodd.

Due to the unstable condition of the rock formations near the bridge, crews drilled holes in the side of the cliff and reinforced them with support rods and shotcrete (dyed and sculpted to match the natural geology of the setting) to prevent further erosion.

Due to project constraints and the technical challenges for design and construction, the Construction Manager/General Contractor (CM/GC) contracting mechanism was utilized. This close collaboration enabled the team to “overcome construction obstacles and allow budgeting issues to be addressed,” notes Dodd. “This type of deliverable technique (CM/GC) also allowed for early procurement of construction materials that were identified as long-lead items and whose procurement was important to the limited winter schedule and job completion.” Making early material orders guaranteed arrival by the construction start date and contributed to the project being completed on time.

Ed Hammontree, P.E., project management branch chief, Federal Highway Administration (FHWA) Central Federal Lands Highway Division, acknowledges that “through the process of CM/GC contracting, Flatirons, Golden Gate National Recreation Area and the Central Federal Land Highway Division of the FHWA were able to collaborate and craft technical and contractual strategies to meet the unique and challenging aspects of this award-winning project at an iconic location.”

“All parties went into this contract with a can-do attitude and sense of partnership,” continues Dodd. This teamwork “helped not only the contract manager (FHWA) and contractor, but also addressed the needs and requirements of the land owner (NPS).”

Hammontree believes the contractor’s professionalism and expertise were key in the “shaping and execution” of the Point Bonita Lighthouse Pedestrian Bridge project. “Flatiron was the right contractor for this unique and challenging project,” he says.

In April 2012, Flatiron completed the pedestrian bridge and the Point Bonita Lighthouse re- opened for business, receiving more than 2,000 visitors on the first weekend. Creativity, collaboration and a can-do attitude contributed to this high-quality, successful project that was delivered under budget and on time.

Owner: Golden Gate National Recreation Area-National Park Service
Construction Manager: Federal Highway Administration, Central Federal Lands Division
Contractor: Flatiron Construction Corp.
Designer: HDR Inc.


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  8. Great Rebuild of bridge!! I visited Point Bonita in July 09 & July 2012. I was stationed at Point Bonita from the last of Sept.1964 into June 1966. My first duty after Boot Camp. The USCG crew stood rotating 6 hour watches with liberty coming at 0800 hrs., after standing the 0000 – 0600 mid-watch. Liberty ended 1130 the next morning. 27 1/2 hrs. of liberty. It was beautiful, when it wasn’t foggy, or raining hard with strong winds making rain horizontal. I was just 18 when I got there, and not quite 20 when I left.