Shoreline Erosion | Coastal Armoring + Engineering

November 14, 2024

Ocean Beach in San Francisco, along the Great Highway. (by Sara Rosado, CC BY-NC-ND 2.0, via Flickr).

California regulators approve huge Ocean Beach seawall – San Francisco Chronicle

Excerpt:
On Thursday, California’s main coastal protection agency approved a $175 million climate-related project that will transform the southern portion of San Francisco’s Ocean Beach despite fierce opposition from some members of the public. A sticking point is a massive seawall that some surfers fear could make the beach disappear.

The California Coastal Commission unanimously approved the city’s Ocean Beach Climate Change Adaptation Project, which will be funded by the city. Created by the San Francisco Public Utilities Commission and other agencies, the plan includes a 3,200-foot-long buried seawall designed to protect a sewage tunnel located along the coast south of Sloat Boulevard. A wastewater treatment plant is right nearby. 

Commissioners expressed concern over many aspects of the plan but agreed that it was the only real option.

“It would be, at the end of the day, very irresponsible of us to take the chance for the tunnel to go down,” said Commissioner Susan Lowenberg, who grew up in the neighborhood.

The 14-foot diameter Lake Merced Tunnel is used to store combined stormwater and wastewater during big storms when the plant is at capacity. It’s particularly vulnerable because that part of the beach is projected to erode by more than 100 feet between now and 2100 because of sea level rise and larger storms that come with climate change, according to a recent study by the U.S. Geological Survey. The city wants to avoid the prospect of sewage spilling directly into the sea from the tunnel.

“If this tunnel were to fail, it would result in a major emergency for this side of San Francisco,” said Anna Roche, SFPUC project manager, at the meeting. “Failure would mean hundreds of thousands of gallons of combined storm water and sewage spilling onto Ocean Beach and hundreds of thousands of San Franciscans unable to flush their toilets…”

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