Presidio Tunnel Tops

San Francisco, CA

Presidio Tunnel Tops

MKA provided civil site design and site structural engineering for the new park built over the Presidio Parkway Main Post Tunnels (housing Highway 101), which connects the Presidio’s visitor center to the Crissy Field waterfront for the first time in nearly 80 years. The park takes advantage of the gently sloped upland area and a dramatic “bluff” that features structured overlooks and offers panoramic views of the surrounding bay as it negotiates approximately 40 feet of grade change. MKA’s engineering innovations include elimination of the typical, massive concrete stormwater detention tanks by leveraging high-performance backfill that doubles as stormwater storage; creation of an inventive layered embankment design for earthquake resilience; and surcharging the site to minimize differential settlement over varying park surface elements (from the rigid tunnels to the soft Bay muds).