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A boat passes Webb Tract farmland as it makes its way through the Sacramento-San Joaquin Delta near Isleton, Calif. (AP Photo/Rich Pedroncelli, File)

Gov. Jerry Brown's administration released two massive documents Monday, detailing its plans to build twin tunnels beneath the Sacramento-San Joaquin Delta and complete the last link of the water system his father began more than a half-century ago.

Minutes later, opponents of the Bay Delta Conservation Plan declared that they will use every available legal and political process to kill it.

The battle will be joined early next year in a series of hearings on the plan and the accompanying environmental impact report, which together comprise tens of thousands of pages aimed, it's said, at improving both water supply reliability and the Delta's environment.

It's likely that years, or even decades, will pass before the issue is resolved one way or the other.

It's Brown's second stab at building a conveyance for Sacramento River water to bypass the Delta.

The first was a "peripheral canal" around the huge estuary, which the Legislature approved more than three decades ago but voters rejected in a subsequent referendum.

Most environmental groups, including the Sierra Club, oppose the tunnels, as they did the canal. But they were joined in the 1982 referendum by San Joaquin Valley farming interests, which didn't like the project's restrictions. This time around, the farmers, who have been hammered by a series of court decisions that restrict pumping from the Delta, are pushing the twin tunnels to make their water supplies more reliable.

That said, the farmers and major urban customers of the state-federal system have not yet committed to spend the $14-plus billion that the tunnels would cost -- and, in fact, have not yet agreed to put up the $1-plus billion to continue project planning.

Money is one of the project's most vulnerable aspects -- not unlike Brown's other pet project, a north-south bullet train.

The project also needs many billions from the federal government and a pending state water bond issue for its ancillary habitat-restoration aspects. Writing the bond issue next year in the Legislature will be a proxy battle over the tunnels.

Brown's Natural Resources Agency touted it Monday as "a significant milestone in the effort to restore ecosystem health and secure reliable water supplies for California." But critics declared that they will litigate ecosystem effects in state and federal courts, focusing on the project's impacts on five endangered fish species and other wildlife.

"Today, we're launching our campaign to defeat this project," Steve Hopcraft, a spokesman for the opposition coalition, declared in advance of a demonstration on the Capitol steps.

As a last resort, the opponents said, they may place the issue before voters via an initiative to erase the state's legal authority to build the tunnels. Project advocates, ever mindful of what happened in 1982, want to avoid another public vote.