SACRAMENTO — The cost of dismantling the dam that created Yosemite's Hetch Hetchy Reservoir and restoring the glacial gorge that John Muir considered one of the national park's scenic treasures could range from $3 billion to nearly $10 billion, according to a state report released Wednesday.
Both critics and supporters of the fiercely debated proposal to return the flooded valley to its natural state seized on the state Department of Water Resources report as good news.
Opponents in San Francisco, which relies on the reservoir for its crystal-clear water and its hydropower, said the lofty price estimates should kill the fanciful idea once and for all.
"This assessment should lay to rest the idea that draining the Bay Area's main source of water warrants further study, particularly in a state that needs more water and more clean power, not less," said Susan Leal, general manager of the San Francisco Public Utilities Commission.
But the group of environmentalists pushing to topple O'Shaughnessy Dam -- the towering wall of concrete completed in 1923 that put Hetch Hetchy Valley under 300 feet of water -- said the 62-page state report underscores that the project, though pricey, is feasible.
"This is a great start," said Jerry Cadagan, chairman of Restore Hetch Hetchy, which champions removal of the dam. "The state has declared that this can be done. That's something a lot of people have been reluctant to admit for a long time."
Cadagan and other dam removal advocates disagree with the state's high price estimates. In recent studies, environmental groups pegged the cost as low as $1 billion. Cadagan said he and other removal boosters "stand by our number."
Gov. Arnold Schwarzenegger ordered the study last year -- a coup for environmentalists who had long been viewed as fringe dreamers for pushing a project largely discounted as a long shot.
Speaking on Wednesday at San Francisco's Commonwealth Club, Schwarzenegger said the report only opened a door to more questions.
"There is still a lot we don't know," the governor said. "It will take awhile."
Although dams on some American rivers have come down in recent years, a Hetch Hetchy restoration would be the largest and most significant attempt to return a valley to its original state.
Gary Bardini, the chief state hydrologist who shepherded the report, cautioned that most of the findings were derived from prior research by universities and advocacy groups that only began to scratch the surface of a complex mix of engineering and public policy questions.
He called the state report "a study of studies."
But the report didn't shy away from suggesting that the water and electricity yielded by the dam and its intricate system of pipelines and power generation stations stepping down the western Sierra Nevada could be replaced.
"From what we have now, we don't see anything that says it can't be done," Bardini said.
Removal of the dam could cost more than $900 million. But the biggest hit would be replacing the Hetch Hetchy's water, which supplies more than 2.4 million Bay Area residents. New off-stream reservoirs might have to be carved, existing dams raised and groundwater tapped at a cost ranging between $1.1 billion and $4.3 billion. Just the price of engineering, legal and administrative costs might hit $1.8 billion.
Boosters say most of the water could be replaced more cheaply by creating groundwater storage and other less costly strategies that the state report failed to consider seriously.
Others say they have heard enough.
U.S. Sen. Dianne Feinstein (D-Calif.), a longtime critic of removing the dam dating to her tenure as San Francisco mayor, said going any further given the astronomical price estimates was "indefensible."
"Draining the reservoir would be far too expensive and leave the state vulnerable to both drought and blackout," Feinstein said, calling it a "serious mistake" to eliminate the 400 megawatts of power that Hetch Hetchy provides when California needs an additional 3,000 megawatts by 2008.
Aside from opposition from Feinstein, the dam removal effort faces a minefield of other political problems. State officials say removal might require congressional action, as well as extensive participation by federal parks and natural resource agencies.
In addition, water managers at Central Valley irrigation districts -- which might be called on to take up some of the slack by storing more water in their Sierra foothill reservoirs for export to the Bay Area -- have vowed to fight.
Although the state report suggested there were "no fatal flaws in the restoration concept" that would preclude further study, the next step of a conceptual review could run $7 million. A fuller environmental assessment of the costs and benefits could cost up to $65 million.
But proponents say that would be money well spent.