Ocean Beach sand going south again
S.F. effort to fight erosion will disrupt traffic on Great Highway
For the next two months, swaths of Ocean Beach in San Francisco will bear a certain resemblance to a life-size playground sandbox.
Each weekday through the end of May, bulldozers, backhoes and dump trucks will dig up and ferry 75,000 tons of sand south from the beach’s northern shores in an effort to temporarily replenish precious coastline lost to the forces of nature and accelerated by the effect of climate change.
It’s a short-term measure the city has undertaken periodically since the early 2000s to combat and adapt to chronic coastal erosion at Ocean Beach south of Sloat Boulevard, where the shoreline’s
attrition poses a mounting threat to critical wastewater infrastructure, natural habitats and beach access.
“The idea is to prevent any emergency situations in this area until a longer-term solution is designed,” said Anna Roche, a climate change specialist and special projects manager with the San Francisco Public Utilities Commission. “In the interim, we’re using these measures to keep the area safe, protect our infrastructure and make the beach a little more accessible.”
The south end Ocean Beach is home to the PUC’s Oceanside Treatment Plant, which processes about 20 percent of San Francisco’s wastewater. Erosion at Ocean Beach poses a significant risk to the Lake Merced Tunnel, a stretch of mostly underground pipeline that runs parallel with the shore, carrying wastewater and storm runoff to the treatment plant. The tunnel is also used to store wastewater during large storms.
Every year, the city takes measurements of how much shoreline is lost to rainstorms, sea level rise and the natural movements of the ocean at the beach’s south end. Those measurements help determine how much sand and sand bags need to be placed in erosion “hot spots” to make up for the loss. One bad storm, Roche said, can result in “25 feet or more of bluff loss.”
Luckily, an overabundance of sand gets deposited naturally each year at the north end of Ocean Beach near the O’Shaughnessy Seawall, so much that it tends to overwhelm the stairwells, promenade and parking lot.
Dump trucks will make about 1,550 trips up and down the Great Highway to deposit that sand and about 700 sandbags at the south end of the beach.
The city is also close to finalizing an agreement with the U.S. Army Corps of Engineers that would allow huge quantities of sand kicked up during the annual dredging of the Golden Gate shipping channel to be placed at Ocean Beach. Roche said the PUC expects to be using that dredged-up sand by as early as next year.
But, as the city admits, merely moving around sand each year won’t solve Ocean Beach’s chronic erosion problem. Additional short-term fixes like the installation of large boulder embankments along the coast have drawn criticism from environmentalists, who cite concerns over habitat degradation.
The city has a permit with the California Coastal Commission to take on smallerscale projects like the sand transfers that’s good through 2021. By then, the city is hoping to have the details of its long-term erosion mitigation and coastal protection plans finalized.
Those plans, Roche said, will include the details for implementing the recommendations in the 2012 Ocean Beach Master Plan, which was written by the San Francisco Bay Area Planning and Urban Research Association, or SPUR, in conjunction with city, state and federal officials.
Ben Grant, an urban design manager for SPUR, said the master plan is meant to guide the city as it adjusts to the inevitability of erosion at Ocean Beach while providing ideas for preserving as much beach access and natural habitat as possible.
“Erosion is already a fact of life at the south end of Ocean Beach, and it’s going to get significantly worse as sealevel rise and climate change set in,” Grant said. The master plan maps out “how to gradually adapt to those changes,” he said.
Among the most ambitious aspects of the master plan is the narrowing and eventual elimination of most of the Great Highway, which snakes along the coastline. Traffic would be rerouted along Sloat and Skyline boulevards. The highway would be replaced with a coastal trail, Grant said, and would give the city “a lot more space to let nature take its course.”
Confronting erosion at Ocean Beach, he continued, will require some sacrifices. “You can have any two: easy flowing traffic, functional infrastructure or a sandy beach — but you can’t have all three.”
Through May, the PUC’s sand caravans will impact traffic on the Great Highway. Southbound lanes of the highway between Lincoln Way and Sloat will be closed to traffic during work hours from 7 a.m. to 4 p.m. on weekdays — sometimes until 5 p.m. when necessary, the PUC said.
South of Sloat, single lanes in either direction will occasionally be closed. And parking areas at the south end of the O’Shaughnessy Seawall, the Sloat parking lot and those south of Sloat will be unavailable during construction.