Sea level rise is a future challenge for Treasure Island

Rising sea levels could affect Treasure Island. Photo by Tristan Sapp.

While the elections are grabbing headlines and our attention, California also faces longer term issues, like the fact that sea levels are rising and we live in an area surrounded by water. Many of us think it’s a problem we’ll have to deal with in the future, but rising sea levels have already claimed one casualty in San Francisco: pier half, just behind the ferry building.

Until 2008, it was where ferries docked from Vallejo. But it was condemned because waves hitting the underside of the deck started breaking it apart.

Will Travis, executive director of the San Francisco Bay Conservation and Development Commission, says Pier Half’s demise is a sign of looming challenges for the Bay Area.

Travis is known as the Bay Area’s oracle of sea level rise. But he’s no Nostradamus.

He doesn’t want us to fear sea level rise. He just wants us to plan for it better – in how we build future developments by the Bay, and protect the ones we have now. In the first part of our two-part series, reporter Julia Scott looks at where the Bay Area is growing in the same places the water level is rising. Today: Treasure Island.

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JULIA SCOTT:  At first glance, you couldn’t pick a worse place to build a city than Treasure Island. The island was thrown together out of soft Bay mud in 1935 for the Golden Gate International Exposition, and it will be the first casualty of liquefaction in a major earthquake. Most of the buildings are in decay: relics of the island’s heyday as a Naval Base during World War II.  

It’s also home to around 1,400 people. They bring their kids to the local Boys and Girls Club after school. And they shop at the island’s only convenience store on their way home. Treasure Island is a mid-Bay outpost - and a small one, at that.  

But that’s not all that engineer Dilip Trivedi sees. When he looks around, he sees up to 8,000 homes, five high-rises, public parks, restaurants and a ferry terminal. That’s the vision proposed by the San Francisco Redevelopment Agency. San Francisco hired the Treasure Island Development Corporation, a group of firms headed by the Lennar Corporation, to make that vision a reality by 2030.

DILIP TRIVEDI: There is a certain character, a certain feel to this island itself as we stand here and you look at Alcatraz, you look at Angel Island, you look at the Golden Gate and the Bay Bridge, and of course the fabulous, any time of the day or night, you come and you see San Francisco’s downtown skyline here.

Trivedi works for Moffatt & Nichol, the engineering firm charged with making this island habitable and secure. The Treasure Island Development Corporation plans to spend more than a billion dollars on infrastructure before the first home is even built.  

TRIVEDI: A lot of the quarters that you see here are going to be rebuilt, there’s going to be housing. The main drive, if you will, as you come off the Bay Bridge itself, that’s going to be the heart of the town itself. There’s going to be Building 1, the great historic building, which is right there buses are going to drop people off there, folks are going to come off the Treasure Island free shuttle out of the homes itself to that center point of the island and take the ferry, take the bus, kiss and ride, carpools – that’s going to be pretty much downtown.

The first challenge they’ll deal with is hard to miss. Treasure Island is only two feet higher than the 100-year flood elevation, designated by FEMA. Although a raised perimeter gives some protection, one corner of the island is regularly flooded by winter waves.  

The project engineers made an interesting decision early on. Rather than build a levee around the island, which would give it the feel of a little Amsterdam, they decided to raise the island itself. Hundreds of tons of dirt, packed tight, will make the ground as solid and resilient as the bedrock of neighboring Yerba Buena Island. It will lift the building foundations three feet above the highest 100-year tide. 

Trivedi says that even when the sea rises over the next century, the homes will be high and dry.  

TRIVEDI: What we are effectively saying is when the sea level rise itself is 36 inches, the community on Treasure Island is still not a levee-protected community, which is far better than most places along even downtown San Francisco and most places around the Bay themselves. 

What made them choose 36 inches as the ideal height? Basically, it’s an educated guess. Here in the Bay Area, cities can decide to build by the Bay and choose their own strategy to protect the development. And when it comes to building levees, no agency factors in the risks of sea level rise - not FEMA, and not the Army Corps of Engineers.  

That means it’s up to developers to look at the science behind sea level rise – and that’s where things get really confusing. The state has adopted a sea level rise projection of 55 inches, or about four and a half feet by 2100. Other predictions are less, or more. NASA’s scientists have said that if either Greenland or the Antarctic Ice Sheet melt away completely, it would raise the earth’s oceans by 16 feet – although it would take many centuries.  

So how do we plan for something we can’t predict? It’s a question that keeps the Bay Conservation and Development Commission’s Will Travis up at night.

WILL TRAVIS: The only thing that is certain is that every time a projection comes out, it’s higher than the last one. So this is one of these things where we don’t know exactly how high waters will rise, we just know that they will rise.

Engineer Dilip Trivedi’s team of engineers is coping with that uncertainty by leaving a 300-foot buffer around the entire three-mile perimeter of the island. It’s designed to give future generations the space they need to build a sea wall.

TRIVEDI: At the point in time where you need 55 inch levees on Treasure Island, there are a lot more problems that are going to happen all around the world, if you will. But within the Bay, Treasure Island will be a pretty safe place to be at.

The same questions facing Bay Area cities also confront planners all over the world. Ten percent of the world’s population lives within low-lying coastal zones, and moving entire cities inland is really not an option.  

At least new development gives us a chance to anticipate sea level rise, and design in a way that adapts to change, says Gabriel Metcalf, executive director of the San Francisco Planning and Urban Research Association.  

GABRIEL METCALF: We want to make sure that if we develop Treasure Island or the Hunter’s Point shipyard, that we are raising the level of the ground above where it is now, above where downtown San Francisco is, so that if sea level becomes a problem, it’s going to be a problem for these new areas a century after it becomes a problem for downtown. 

It’s hard to imagine San Francisco underwater, let alone Silicon Valley or the East Bay. But these are scenarios that experts say we ought to be thinking about today. And how well cities plan could determine whether coastal zones continue to thrive… or become places of mass desertion.

On Treasure Island, I’m Julia Scott for Crosscurrents.  

Look for Julia Scott’s stories about sea level rise and its impacts on development in Sunday’s Bay Area News Group papers.