Construction on the Presidio Tunnel Tops project in San Francisco recently broke ground. The development represents fourteen acres of new national parkland that will be created atop highway tunnels, with dramatic views of Golden Gate Bridge, the Bay, the Presidio, and the San Francisco skyline.
The $118-million project is being led by the Presidio Trust, in collaboration with the National Park Service and the Golden Gate National Parks Conservancy. Swinerton Builders is leading construction.
Other members of the project team include James Corner Field Operations (landscape architect); EHDD (architect); Miller Pacific (geotechnical engineer);WOOD (environmental engineer); Stok (sustainability); MKA (civil and site structural engineer); Holmes (building structural engineer); PAE (MEP engineer); HLB (lighting designer); DD Pagano (irrigation designer); Fluidity (water feature designer); and KKA (signage designer).
The project is an example of a growing trend to turn derelict highways and rail lines into public green spaces and parkland. When complete in fall 2021, the new Presidio destination will include gardens with native vegetation, connective pathways, scenic overlooks, a campfire circle, picnic areas, and a Youth Campus with a three-acre interactive play area designed to connect urban kids with nature.
The site is immediately adjacent to the Presidio Visitor Center, which opened in 2017, and a planned transit center.
There were some delays in the project, which was probably the biggest challenge prior to ground breaking, says Paula Cabot, senior project manager for Tunnel Tops, Presidio Trust. Greg Moore, CEO emeritus and special advisor, Golden Gate National Parks Conservancy, says that “any project involving federal, state and local entities can hit delays including the transition of project management from the highway building phase to the park building phase.”
The project consists of 6,528 sq-ft of new construction and 13,055 sq-ft of remolded or rehabilitated work. It will also use approximately 96,000 cu-yds of soil about roughly 200,000 plants.
Currently on the project, the soil surcharge continues to settle, with final settlement forecasted early next year, after which there’ll be a buildup of construction activities, says Cabot. She says the quality of the soil for building parklands needs to be much higher grade than for most simple construction sites, so carefully sourcing soil is important and tricky.
“The soil is tested for chemicals of concern (COC), percolation rate (for drainage) and gradation (particle size for compaction),” says Cabot. “Later, the horticultural grade top soil with the right chemistry, texture, structure and organic content to nurture both native California species and climate-adapted ornamental species will be placed during the build phase.”
While crews wait for the soil to settle, they are laying groundwork for utilities, and roads for vehicle access. Cabot says they continue to have weekly meetings with the project team. “As you’d expect, coordination, communication and change management are woven into discussions about logistics and design issues,” says Cabot.
Liz Messana, Swinerton senior project manager, says that during peak construction, there will be about 50 to 70 workers on site daily.
Space for the Presidio Tunnel Tops project came from the transformation of the former Doyle Drive highway into the Presidio Parkway. The design was shaped by input from over 10,000 community members. While the old highway once cut off the northern waterfront from the rest of the Presidio, the new parkway places key sections in “cut and cover” tunnels, allowing for new parkland above.
When complete, visitors will be able to walk from Crissy Field to the Presidio’s Main Post for the first time in 80 years, enjoying dramatic views along the way.
The Tunnel Tops project is made possible by philanthropic efforts led by the Golden Gate National Parks Conservancy. The campaign leadership and committee members have mobilized the effort to raise $98 million toward the campaign goal. During the “quiet” phase of the campaign, $86.7 million has been raised. A public campaign for the community will kick off in spring 2020.