At the project’s other end, workers are coming within 15 ft of historical buildings, including 100-yr-old army structures. This is another reason for the CDSM technique instead of pile-driving, which could cause vibration damage to nearby structures.

The project is a collaborative effort by the California Department of Transportation (Caltrans), the San Francisco County Transportation Authority, and the Federal Highway Administration. Flatiron is the design-build lead for Golden Link Concessionaire, LLP, which under the P3 contract will design, build, finance, operate and maintain the project for 33.5 years.

“The P3 method allows us to reduce the overall schedule time that is required for design and construction,” says Tolp. “It also gives us the ability – particularly on a site as complicated as this – to address some of the challenges we see during the design phase, and over life of project respond to things that may require changes to design faster.”

HOCHTIEF and Meridiam are the project's developers and equity partners. HTNB Corporation is the lead engineering firm on the project.

The total cost of Phases I and II is $1.4 billion over the next 30 years. Construction began in late 2009 and will be complete in 2015.