Presidio Parkway Construction in Full Swing
Construction is in full swing on Presidio Parkway, a major overhaul to the existing Doyle Drive roadway, built in 1936 to connect the Golden Gate Bridge to San Francisco via an elevated roadway over the then-operational Presidio military base. The public-private partnership project is California’s first transportation P3 project enacted under the most recent P3 legislation.
Flatiron leads the design-build team with Kiewit for Golden Link Concessionaire, LLP, who will design, build, finance, operate and maintain the project for the next 33.5 years. Along with seismic improvements that make the parkway earthquake-safe, the new parkway will improve traffic safety and allow pedestrians and bicyclists to cross over or under Doyle Drive on a network of beautifully landscaped bike and trail paths.
The seismic improvements alone are an enormously important part of the project. The 1.5-mile project corridor is located in a highly seismically hazardous area, and because it is designated a recovery route in the event of a disaster, it must adhere to stringent design standards.
“There are provisions within our contract that the parkway has to be designed to be usable again within 72 hours after a significant earthquake,” said assistant project manager Adam Mathews. “People need to be able to exit the city after an event, and emergency workers need to be able to get in to the city quickly to help.”
Cement deep soil mixing, or CDSM, is one of the features of the design; crews drill cement in the ground underneath the embankments and the tunnels on the project in order to prevent the structures from breaking off and floating in the bay during an earthquake. To date, Flatiron has completed approximately 40 percent of the CDSM while continuing work on three covered tunnels and six bridges, as well as a high viaduct at the other end of the project site. Foundations for the high viaduct—a tall, lengthy bridge—is approximately 80 percent complete, with excavation for the tunnels and other work being completed in tandem.
“It’s an extremely compressed project timeline,” adds Adam, “so we’re basically building everything all at the same time, in a very small area.”
The project area runs through a national park situated on the old Presidio military base, a unique location that presents a number of challenges and represents multiple stakeholders who are all heavily involved in the project. Golden Link Concessionaire, LLP, the Presidio Trust, the National Park Service, San Francisco Transportation Authority, Caltrans and many others are all involved in the process of designing and building the project, making it exceptionally challenging for everyone involved to continue daily progress. There has been a monumental effort from the team just to get construction started, with a major ramp-up of construction over the fall.
“This project is one of the most challenging that I have ever been on,” adds Adam, “But we do get to look at the Golden Gate Bridge every day, and over the summer we were able to see the America’s Cup racing teams out on the bay.”
Flatiron began work on the second phase of the project in March 2013, and the Presidio should be open to traffic in 2015.
Want more Presidio Parkway? Check out more photos of construction here.