Solano County

Hydroids flourish in North Bay Aqueduct

By From page A1 | October 10, 2012

VACAVILLE — Small creatures called hydroids are putting a bit of a squeeze on the local Sacramento-San Joaquin Delta water delivery system.

There’s a several-inches-thick coating of the creatures inside the concrete North Bay Aqueduct pipe, with this coating extending for a quarter-mile beyond the Barker Slough pumps in eastern Solano County. This has cut the maximum amount of water that can flow through the pipe from 154 cubic feet per second to 135 cubic feet per second.

“It’s not a huge problem,” Solano County Water Agency General Manager David Okita said. “But it’s something we’d like to figure out — if it’s cost-effective to do something with it or if it’s more cost-effective just to live with it.”

So far, water officials haven’t found the answer to what they call “the biofilm problem.”

The Solano County Water Agency Board of Directors will hear a presentation on the topic Thursday. It meets at 7 p.m. at agency offices, 810 Vaca Valley Parkway.

Hydroids are plant-like animals related to jelly fish and corals. Okita said they look like tree branches a few inches long.

Shipping and ballast water has introduced numerous species to Bay Area waters since the Gold Rush, according to a U.S. Fish and Wildlife Service report.

Hydroids got a new home when the NorthBay Aqueduct opened in 1989. It is a 6-foot-diameter concrete pipe buried about 20 to 30 feet deep that delivers Delta water from Barker Slough to Fairfield, Vacaville, Vallejo and Napa. It is part of the State Water Project.

Each year, the pipe gets drained so maintenance workers can enter it through manholes, Okita said. Maintenance workers discovered the hydroids in 1999, at a time when local cities used less water. Peak water demand has now reached what the hydroid-restricted aqueduct can deliver, he said.

“That first quarter-mile (of pipe), the hydroids are feasting on whatever is in the Delta water,” Okita said. “But eventually, they eat it all up. That’s why you don’t see hydroids all the way to Napa.”

One possible way to defeat the small invaders is using chemicals, Okita said. But, since this is drinking water, there are limits to what types and what concentrations of chemicals can be used, he said.

Another possibility is running a mechanical cylinder with bristles through the pipe to remove the hydroids, he said. That method worked when attempted a few years ago. But the hydroids grew back in a couple of months, he said.

Yet another possibility is lining the concrete pipe with epoxy or teflon, Okita said. This too has a downside.

“It’s very expensive and you have to re-coat the pipeline every five to 10 years,” Okita said.

At this point, there’s no hydroid problem at other Delta pumping facilities that might give clues to a solution, Okita said.

Fairfield and Vacaville get water from both the Delta and from Lake Berryessa reservoir in Napa County.

Reach Barry Eberling at 427-6929, or [email protected] Follow him on Twitter at www.twitter.com/beberlingdr.

Barry Eberling

Barry Eberling

Barry Eberling has been a reporter with the Daily Republic since 1987. He covers Solano County government, transportation, growth and the environment. He received his bachelors of art degree from the University of California, Santa Barbara and his masters degree in journalism from the University of California, Berkeley.

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