Subscribe / Renew
|► Subscribe to our Free Weekly Newsletter|
|home||Welcome, sign in or click here to subscribe.||login|
|print email to a friend reprints add to mydjc|
February 6, 2023
Magnusson Klemencic Associates
Project: Presidio Tunnel Tops park
Client: The Presidio Trust
The design of San Francisco’s new Presidio Tunnel Tops park provides a preview of the future of civil engineering. This 14-acre, $118 million landmark destination built atop two highway tunnels is the newest addition to America’s National Park system.
Magnusson Klemencic Associates created forward-thinking design solutions to restore the natural landscape, overcome challenging site conditions, improve the environment, reconnect visitors to nature, prepare for earthquakes and what the future may bring in climate change, and more.
The engineers put sustainability and resilience at the top of the criteria list. The park’s design also focuses on the users and harmonizing with nature instead of trying to conquer it, minimizing traditional concrete infrastructure that would detract from the beauty of this popular park with a long history.
Reshaping the site’s steep bluff into a gradual embankment created the opportunity to build an ADA-compliant path winding nearly two miles throughout the park, making it accessible to everyone. Replacing the previous 75-year-old elevated highway with tunnels below the park created an elegant and unobstructed pedestrian connection from the hilltop Presidio parade grounds to the bay’s waterfront for the first time in nearly 80 years.
The PTT includes many innovations and firsts in its civil engineering design. An innovative restorative water management system uses a specially engineered backfill throughout the park to restore the park’s natural hydrologic function, recharging the groundwater while reducing stormwater runoff instead of using typical massive concrete stormwater detention tanks.
A resilient design trifecta anticipates potential climate change, resisting, absorbing and adapting to saltwater intrusion concerns, groundwater rise, and increasing precipitation. The innovative layered embankment design uses a variety of newly developed materials to fill over the rigid tunnels and soft bay mud, providing added resilience against liquefaction during a seismic event, reducing the load on the tunnels and solving the problem of differential settlement.
The reimagined park now features areas that provide a traditional National Park camp-like experience in an urban setting. A campfire circle features seating for up to 75 people and space for ranger talks and community events. The Cliff Walk and scenic overlooks thread the edge of a 30-foot-tall bluff, providing sweeping views of the Golden Gate Bridge, Alcatraz and the San Francisco Bay. Visitors can enjoy views, watch performances in the amphitheater below from the stepped lawn terraces overlooking the bay, and use the new picnic area. The park also includes gardens and natural plantings to provide a place for migratory birds to rest, play areas for children, and facilities for environmental learning and youth programs, with more to come in future phases to maximize the use of this park.