Treasure Island, San Francisco, California, to be protected from sea level rise

Treasure Island to be protected from rising seas

by John Upton, San Francisco Examiner Staff Writer, January 21, 2009

Vulnerable: Parts of San Francisco’s man-made island may be elevated with fill to protect developments scheduled to be built in 2010. Getty Images File Photo SAN FRANCISCO – Dirt and other fill may be piled onto parts of Treasure Island to protect planned buildings from sea level rise due to climate change and other factors.

A multibillion-dollar plan for the 450-acre man-made island — including a ferry terminal, retail strip, three hotels and 6,000 new housing units, including a 60-story residential tower — was adopted in 2006 by The City.

But the low-lying island is vulnerable to floods if seas rise due to climate change, according to Kheay Loke, a developer with Wilson Meany Sullivan, which is partnering with Lennar Corp. on the project.

The flood risk will be greatest if rising seas coincide with a high tide and large storm, according to Loke.

Loke and a handful of engineers and city officials presented options last week to the Treasure Island Development Authority Board of Directors for protecting new buildings against climate change-related flooding.

To protect new buildings from floods, fill will likely be dumped beneath planned development sites, according to Loke.

The fill will be excavated from some of the 300 acres of island that’s slated to be used for parkland and sports fields, and additional fill will be imported to the island, according to Loke.

“It’s all about raising grades to enable gravity drainage, as opposed to relying on levees for protection,” Loke said.

The developers could also choose to build sea walls — which would serve the same function as levees in the Central Valley and New Orleans — around the island to protect against flooding, authority documents show.

The Board of Supervisors will ultimately decide how to protect the island from a potential 3-foot sea level rise over 70 years, according to Jack Sylvan, who oversees public-private partnership projects for The City.

Property taxes could be set aside to build sea walls, or take other flood-protection measures, if seas rise more than expected, according to Sylvan.

“The City is working on how it will address sea level rise in the future, assuming it does in fact happen,” Sylvan said.

Infrastructure work, including grading and seawalls, could begin by late 2010, according to Sylvan. Building construction is expected to start 18 to 24 months later, he said.

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