A nearly $1 billion project that will insulate 1.4 million East Bay residents from the worst of drought is ready for business after completion of a 10-day test run last week.

The Freeport Regional Water Project, a joint venture between the East Bay Municipal Utility District and a Sacramento-area water agency, will supplement East Bay water supplies in about three of every 10 years to limit dry-year rationing to no more than 25 percent.

In 2008 and 2009, when East Bay residents were asked to use 15 percent less water, the district likely would not have imposed drought restrictions if the plant were online, said Michael Tognolini, EBMUD's manager of water supply improvements.

Testing was a success, he said.

"This is the first time we ran it at full capacity," he said. "We're pleased. It's a major milestone."

On the bank of the Sacramento River, the $121 million centerpiece of the project -- the pumping plant -- is meant to look something like a fish.

A plaza, which is near the end of a public bike trail, sits at the base of a "poetry wall" that displays etched phrases such as, "Water carries the memory of mountains into the sea's forgetting."

The word "river" is spelled both normally and backward to reflect the ebb and flow of a tidally influenced river.

In the back, the concrete wall above the river is finished to resemble scales. Below the scales, a stainless-steel screen with a mesh tight enough to prevent a quarter from passing through extends into the river to keep tiny fish from being sucked into the pumps.

Water passes through the screens into an open room, where catwalks cross over a series of chain-driven paddles that scrape silt to one side while propeller-like intakes pull water out of the river.

Upstairs, in the cavernous concrete building, a series of eight 2,000-horsepower pumps stand ready to send water to Sacramento and the East Bay.

The Freeport Project is the culmination of a decades-long attempt by the Oakland-based water district to diversify its water supply.

The district relies on the Mokelumne River, where its dams and pipelines that have been serving the East Bay since 1929.

In 1968, the district signed a contract for American River water but ran into stiff opposition from environmentalists and Sacramento residents who feared that the river would be dewatered.

After a lengthy court fight, the district pared down its demand for water and agreed to move the intakes downstream of Sacramento. The Sacramento County Water Agency joined the project.

The East Bay's share of the $900 million project is $460 million, or slightly more than half. The Sacramento agency, whose share is $440 million, plans to use the Freeport pumps as a regular water supply and not just for drought insurance.

Regular water deliveries to Sacramento are expected to begin after canal work is done in November, said Hal Vandeloo, a civil engineer with the Sacramento agency.

Because the project was expensive and EBMUD will use relatively little water, the cost of water from Freeport comes in high for the East Bay -- about $800 per acre-foot, much higher than the market cost of water most of the time.

But EBMUD figured that without the Freeport project, a severe drought like the one that struck in 1976 and 1977 could force customers to cut water use by more than half.

If such a drought struck again before 2020, the district expects that rationing would be no more than 25 percent.

The water district is working on a plan to get through the year 2040.

Under that plan, the district is considering water conservation measures and other alternatives, but it figures that it will either have to desalinate water or raise its dam on the Mokelumne River, a possibility that has already led river advocates to sue.

Mike Taugher covers the environment. Contact him at 925-943-8257.