SAN FRANCISCO -- San Francisco city officials Thursday gave approval to a $4.4 billion project to seismically retrofit the Hetch Hetchy water system that provides water to some 2.5 million customers in the Bay Area.

A series of more than 80 individual projects is intended to replace aging infrastructure and make the system safe in the event of a major earthquake, said Ed Harrington, general manager of the San Francisco Public Utilities Commission, which manages the system.

The Hetch Hetchy system crosses three major earthquake fault lines -- Calaveras, Hayward and San Andreas -- delivering water from the Sierra to San Francisco, Alameda, Santa Clara and San Mateo counties.

Following Thursday afternoon's certification by the city Planning Commission of the final environmental impact report for the regional Water System Improvement Program, the Public Utilities Commission unanimously approved a version of the program intended to address some concerns of environmental groups, but which has still been criticized.

Hetch Hetchy currently delivers an average of 265 million gallons of water each day to the Bay Area. About 85 percent of that water comes from the Tuolomne River, which originates in Yosemite National Park.

According to the Public Utilities Commission, by 2030 the amount will need to increase to 300 million gallons per day.

Environmental groups have concerns that any more diversion of water may damage the Tuolomne River and severely impact fish stocks.

The version of the program approved today will maintain the 265-million-gallon average until 2018, but will include a provision for additional diversion following severe drought conditions.

The Public Utilities Commission intends to study how it can make up the remaining 35 million gallons through additional local conservation, recycled water and groundwater projects.

Diverting more water from the Tuolomne River "would exacerbate the decline of Chinook salmon and steelhead trout," said Peter Drekmeier of the Tuolumne River Trust. "And they're already in seriously poor condition."

Jennifer Clary of Clean Water Action said of the environmental impact report, "The fact of the matter is cumulative (environmental) impacts have really been ignored in this document."

Harrington called the plan "a reasonable outcome," balancing the health of rivers and the people that rely upon them with the needs of water customers, he said.

He also said construction would create an estimated 20,000 Bay Area jobs.