In late October, SPUR shared with the public a set of draft recommendations for the Ocean Beach Master Plan, a long-range vision for managing coastal erosion, infrastructure, access and ecology on San Francisco’s western coast. Though the beach faces many challenges, it is south of Sloat Boulevard that the issues come to head. This is where the ocean’s erosive scour is worst, and it’s also the home of the Lake Merced Tunnel and other expensive, recently built wastewater infrastructure. The beach here has been degraded by emergency armoring and exposed fill, limiting access and threatening both natural communities and a beloved local surf break. In short, it's a mess.
But from a planner's point of view, a confluence of challenges is an opportunity to solve for a number of different objectives at once. Of the six big ideas in the draft recommendations, here are two that propose the most significant — and exciting — changes to streets, public spaces and coastal management at the southern end of the beach:
KEY MOVE 1: Reroute the Great Highway behind the San Francisco Zoo via Sloat and Skyline boulevards
Stop defending what we don't need
To date, the city has been defending the Great Highway South of Sloat Boulevard with boulder revetments. Many officials agree that the road is a proxy for a much greater concern: the Lake Merced Tunnel, a 14-foot underground sewer and stormwater pipe that runs underneath the highway. The road is lightly traveled and frequently closed (most notably the southbound lanes were closed for nearly a year in 2010). Rerouting traffic from the Great Highway to Sloat and Skyline (which have capacity to spare) would allow a more flexible approach to coastal protection and create major restoration and recreation opportunities.
Tame an unsafe and overwide street
Sloat Blvd is six lanes wide, with diagonal parking in the median. Zoo visitors often park there and jaywalk across the street with small children. Re-routing the Great Highway inland would allow significant improvements to Sloat Boulevard, like moving parking to the south side along the zoo and adding a first-class bike route. The L-Taraval Muni line could be extended one block to terminate adjacent to the zoo. Counterintuitively, auto access to the region could improve, as traffic controls are upgraded and this important link is no longer subject to closure by erosion or flood.
Create a new gateway to the zoo and the coast
Drivers, cyclists and Muni riders would all arrive at the south side of Sloat, where they could visit the zoo and access the coast without crossing any streets. A new access point near the pump station would provide bike parking, restrooms and information, while a restored Fleishhaker pool house could host a visitor center with food and interpretive elements. Sloat's neighborhood businesses could thrive on a safe, attractive seaside street.
Give us back our coast
Removing the Great Highway South of Sloat would offer an amazing recreational resource for cyclists, pedestrians and beach users while allowing for a healthier ecosystem. Today's landscape of asphalt, rubble and boulders would be gradually transformed into a coastal trail linking Fort Funston to the rest of Ocean Beach and beyond, reminiscent of recent improvements at Land's End and Crissy Field. Infrastructure would remain, but the structures used to protect it would be designed with access, aesthetics and natural resources (like the bank swallow) in mind.
KEY MOVE 2: Introduce a multi-purpose coastal protection/restoration/access system
Remove the road, and take advantage of the opportunity
Unlike the Great Highway south of Sloat, the Lake Merced Tunnel is a significant piece of infrastructure and worth protecting in the coming decades. West of the zoo, the road is perched atop an erodable berm of construction fill, well above the pipe. Letting that vertical space go would allow a much more flexible approach to coastal protection. The solution outlined in the draft is conceptual and will require considerable study to ensure its feasibility, but the underlying ideas represent a new and more nuanced approach to the problem of erosion at Ocean Beach.
Armor the Lake Merced Tunnel with a low-profile structure
The Lake Merced Tunnel sits much lower than the roadway. If it can be protected with a low wall, cap or internal reinforcement, it can become a sort of "speed bump" under the beach. This is a significant engineering challenge, as it needs to be protected from wave energy, flotation forces (it is mostly empty most of the time) and seismic forces.
Layer flexible, dynamic structures over hard structures
The structure protecting the Lake Merced Tunnel would be covered by a berm of cobble, stones that range from the size of marbles to that of softballs. These structures, modeled on natural cobble beaches, can be shaped dynamically by wave action and excel at dissipating waves energy. A second cobble berm farther inland, would protect existing force mains and high ground near the Fleishhaker Pool building. Large quantities of sand would then be placed over the cobble, providing a first line of protection and a sandy beach most of the time.
Restore the surface, give us back our coast
If infrastructure protection alone is the goal, then a traditional seawall or revetment would do. But this plan's goal is to serve multiple objectives simultaneously, and the recommended approach allows Ocean Beach to protect infrastructure while also improving recreational access, ecological function and character, in keeping with its status as a national park. Regular placement of sand and revegetation would offer an accessible beach environment, with a spectacular trail connecting Sloat Boulevard to Fort Funston. Cobble is passable and attractive even when sand has been washed away, as it might be in major storms. And the San Francisco Zoo could find a new expression of its conservation values through an improved relationship the watershed and the coastal ecosystem.
The Ocean Beach Master Plan will be finalized in early 2012. To view the complete draft recommendations, see the slideshow below: