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America's Cup Plan to Curb Invasive Seaweed: Scrape Piers by Hand

The latest proposal to prevent the spread of invasive seaweed as San Francisco prepares to host the America's Cup would have scuba divers painstakingly remove the pest by hand from old piers before they are torn down.

State water quality regulators had ordered the organizers of the sailing event to develop a detailed plan for preventing Undaria pinnatifida, an invasive species of kelp, from releasing spores as infested structures are demolished.

The seaweed attaches itself to piers and other hard surfaces and can grow to 10 feet. When disturbed, Undaria can release clouds of spores that float with currents to establish new populations. Scientists have warned that the seaweed could devastate native kelp populations if it spreads throughout San Francisco Bay.

Under the proposal, divers would encase Undaria with a plastic trash bag while it is still attached to a pier and then use a putty knife to scrape the vegetation away from the wood or concrete.

“The idea is to remove Undaria prior to any stress, like vibrations due to removal, in order to reduce the likelihood of spore release,” said Chela Zabin, a scientist with the Smithsonian Environmental Research Center who discovered the pest in San Francisco Bay in 2009 and advised regatta officials on strategies for preventing its spread.

Bags of seaweed would then be handed to workers on the shore and removed from the area.

Deb Self, executive director of the nonprofit Baykeeper, who has been working closely with regatta organizers to help minimize environmental impacts from the event, warned that the measures might be insufficient to prevent the seaweed's spread.

"They’ve put out a good draft control plan, but it’s probably not detailed enough for the [State Water Resources Control Board] to sign off on," Self said in an email. "The city probably also needs to consider using underwater filter fabric to prevent the release of Undaria, concrete dust and other pollutants into the Bay during construction and demolition.”

It is not known how much the organizers' proposal would cost, according to Port of San Francisco spokeswoman Renee Martin. The port is taking a leading role in helping prepare for the sailing event, which would see rotting piers replaced with new docks. The event is supposed to pay for itself, but San Francisco could agree to help subsidize it if a special fundraising committee doesn't raise enough money.

To prevent invasive seaweed from being brought into the bay from elsewhere, regatta organizers also proposed using high-pressure washers or steam cleaners on any docks, moorings, anchor lines and other infrastructure before it is relocated into the bay.

Additionally, barges and other work vessels would have their hulls cleaned before entering the bay.

Water board staff will consider the proposal in the coming months, before deciding whether it will be presented to board members, according to Xavier Fernandez, a project manager at the agency.

A final environmental impact report dealing with the America’s Cup, including measures for controlling the invasive seaweed, could be published in late November or early December, with certification by the San Francisco Board of Supervisors planned before the end of the year, according to Joy Navarrete, an official with the San Francisco Planning Department.

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