New sea-level rise projections have increased tenfold the cost to protect the San Francisco International Airport from flooding.
In 2015, the Board of Supervisors gave initial approval to a $58 million shoreline protection program to protect SFO from sea-level rise.
But on Wednesday, the board’s Budget and Finance Committee approved an updated program that will now cost $587.1 million.
City officials attributed the increase to new sea-level rise estimates and guidelines issued by the State of California in a March 2018 report called “Sea-Level Rise Guidance.”
The 2015 program relied on sea-level rise estimates in 2012 that had the airport planning to protect the facilities from a rise of 11 inches.
The new program now has the airport anticipating a sea-level rise of 36 inches.
“The updated Shoreline Protection Program proposes construction of a new shoreline protection system around the entire perimeter of the Airport, including along Highway 101, and would protect the Airport assets and runways, with a 99.5% level of confidence, to approximately 2085,” an SFO study on the program said.
That includes constructing “7.6 miles of new sheet pile walls at most of the reaches; new concrete walls at the San Bruno Channel and Millbrae Channel; and 2.7 miles of concrete wall on the Airport front side along Highway 101.”
Additional costs also come from the need for “environmental mitigation, specifically for wetland and Bay fill.”
The Airport comprises about 5,171-acres of land and includes an eight-mile shoreline along the west side of the San Francisco Bay.
“A report released by the San Francisco Bay Conservation Development Commission in 2011 suggested that 72 percent of the Airport would be at risk from a 16-inch sea level rise,” the study said. “Currently, more than six of the eight miles of shoreline are protected by engineered earthen berms, concrete seawalls, and vinyl sheet piles that were constructed in the early 1980s.”
SFO sees about 55.8 million passengers a year and employs about 42,800 workers.
The airport plans to pay for the project using revenue bonds backed from money it generates from airlines and from non-airline leases and concession revenues.
Since the airport is borrowing money, the cost of the project plus the interest will bring the total project cost to $1.5 billion.
The full board is expected to vote on the program Tuesday. Technically, the board is being asked to determine the project is “fiscally feasible and responsible.” With approval, the Planning Department can begin an environmental review of the project. Future approvals would be needed for the program to begin.
“I just have to say this is somewhat frightening,” said Supervisor Sandra Fewer. “The fact that we are now anticipating for a sea level rise of 36 inches, rather than 11 inches from the 2015 plan.”
“I do think that this isn’t the last time we will see an assessment that we might have to recalibrate how much more protection we will need,” Fewer continued. “I think we have seen in these past years and in these recent past years that mother nature actually has the last word on this.”