Water for Palo Altans, and 2.3 million other Bay Area residents, flows down from the Sierra through a series of pipes and tunnels, crossing five seismic faults.
An earthquake could cut off water supplies for up to 60 days, a 2000 study found.
To boost the reliability of its complex system, and provide additional supply for the future, the San Francisco Public Utilities Commission (PUC) has launched a $4.3 billion series of projects known as the Water System Improvement Project.
Palo Alto could be responsible for a contribution topping $130 million, Vice Mayor Larry Klein said Monday at the first of two public discussions this week on the effort.
Klein called the plans "big, very, very important and very, very complicated."
The council discussed the project Monday and the San Francisco PUC hosted a public forum Wednesday so the public could respond to the master environmental report.
Most controversial is the proposal to take an additional 25 million gallons of water per day from the Tuolumne River. Providing more water than is currently needed would have a potential "growth-inducing" effect, Assistant Utilities Director Jane Ratchye said.
The project also includes installation of a connection between two major supply pipes near Gunn High School, Ratchye said.
Several council members said they wished the San Francisco PUC had focused on seismic safety rather than on boosting water supply. They called for additional conservation rather than taking more water from the Tuolumne River.
"We pride ourselves as environmental leaders (in Palo Alto)," Klein said. "But we're not leaders in conserving water ... because by and large we have nice lawns."
"We're not going to get a lot of sympathy if there is a severe drought."
Several council members also said they were surprised the report didn't include the effects of global warming on the water supply.
Councilman Peter Drekmeier did not take part in the discussion because as a recently hired program director for the Tuolumne River Trust it's his job to advocate for the river.
He spoke Wednesday before about 50 people who attended the San Francisco PUC hearing.
"Our organization and every other conservation organization I'm aware of supports the seismic upgrades to the Hetch-Hetchy system," Drekmeier said. "What we are adamantly opposed to ... (is) the equivalent of 1,000 large swimming pools every day pulled from this wonderful, wild and scenic river."
The water loss would harm fish populations, increase the effects of water contaminants and reduce the river's availability for recreation, the group has said.
Palo Alto resident Mary Jane Marcus said she was so committed to conserving water to prevent the additional diversion she'd nearly shower outdoors and knock on neighbors' doors to spread the word.
The council will finalize its formal comments to the San Francisco PUC at its Monday meeting.
The master environmental report for the project is available at www.sfgov.org/site/planning_index.asp?id=37672. Comments are due by Oct. 1. Many of its components will also require individual reports.
Palo Alto is independently pursuing a separate water-supply project to construct an underground reservoir and repair or install several groundwater pumps. That project will appear on the November ballot as an advisory measure because the reservoir would be located under El Camino Park, requiring the dedicated park's closure during construction.