A $4.4 billion upgrade program has been approved by the San Francisco officials to safeguard the Hetch Hetchy, the Bay Area's largest drinking water system from drought or a catastrophic earthquake.

Both San Francisco's planning and public utilities commissions, despite opposition from some environmental groups have approved the upgrade though they have put off plans to divert more water from the Tuolumne River for another decade.

The original proposal of diverting an extra 35 million gallons a day was strongly opposed by environmentalists, fishing groups and the Modesto and Turlock irrigation districts which would have taken up to 25 million gallons per day from the Tuolumne.

Peter Drekmeier, Bay Area program director for the Tuolumne River Trust said, "This is a major victory for the wild and scenic Tuolumne River. A year ago, we faced a proposal to divert an additional 25 million gallons of water per day from the Tuolumne -- enough to fill 1,000 swimming pools. We've come a long way."

The San Francisco Public Utilities Commission officials say is necessary to keep the system functioning after a major temblor. The water system which cuts across five major fault lines could be seriously damaged in a serious earthquake warned the SFPUC officials.

The water comes primarily from the Hetch Hetchy Reservoir in Yosemite National Park to distribute to 2.5 million customers in San Francisco and its neighboring counties.

Digging a 5-mile tunnel under the bay for water supplies and replacing a seismically unsafe dam at the Calaveras Reservoir were part of the program which involves 85 individual projects, including laying sections of redundant pipeline, to maintain water supplies for the city Public Utilities Commission's 2.5 million customers in San Francisco, Santa Clara, Alameda and San Mateo counties. The projects are scheduled to be completed by 2014.

Allen Short, general manager of the Modesto Irrigation District said, "We will continue to review the plan, but are pleased that there is talk of San Francisco exploring drawing water from resources other than the Tuolumne."

Opposition to the program comes as environmental groups don't want to see additional water diverted from the Tuolumne River or Alameda Creek as they feel these will harm steelhead trout and other wildlife. Municipal water customers, like the cities of San Jose and Santa Clara, are concerned about whether the plan will ensure adequate long-term water supplies.

California is experiencing a drought and many Southern California water districts are planning to ration water this summer. The SFPUC General Manager Ed Harrington said they plan to rely more heavily on conservation measures such as using recycled water from golf courses and parks and by tapping new groundwater sources. The city Board of Supervisors also will be asked to set requirements on low-flow toilets, shower heads and faucets, Harrington said.

Michelle Reimers, a TID spokeswoman said, "TID fully supports San Francisco's need to improve the safety and reliability of their drinking water supply system through the seismic upgrades. San Francisco has acknowledged that they do not have rights to divert any additional water from the Tuolumne. Additional diversions would only be possible if TID entered into a water sales agreement with San Francisco. TID has no plans to sell any water to the city and county of San Francisco."

Those opposing the proposal have 20 days to appeal Thursday's approval of the environmental report to the Board of Supervisors. Several environmental advocates said they are undecided on whether to appeal.