(10-12) 04:00 PDT Washington --

More than half of all industrial and municipal facilities across the country dumped more sewage and other pollutants into the nation's waterways than allowed under the Clean Water Act, according to a report released Thursday by an environmental group.

California was among the 10 states with the highest percentage of facilities leaking more pollutants into waterways than their Clean Water Act permits allow, according to data from the U.S. Environmental Protection Agency obtained by the environmental group, U.S. PIRG.

California also had the dubious distinction of having the most large-scale violations - or "exceedances" - of Clean Water Act permits of any state. The large-scale violations are those that exceed the permitted level by at least 500 percent.

Environmentalists said the figures show that industrial plants and municipal wastewater facilities continue to flout the law because of insufficient policing by federal regulators.

"The bottom line is the Bush administration isn't doing enough enforcement of the Clean Water Act," said Christy Leavitt, clean water advocate for U.S. PIRG, a federation of state Public Interest Research Groups.

EPA officials defended the agency's record, saying they had taken enforcement actions resulting in $8.8 million in fines last year for those caught violating the Clean Water Act.

'Strong enforcement'

"We will continue to aggressively enforce our nation's environmental laws through effective compliance assistance and a strong enforcement program," EPA spokeswoman Roxanne Smith said.

In Northern California, the cities of San Francisco, South San Francisco, Pacifica, Sausalito, American Canyon, Manteca, Stockton and Watsonville reported exceeding their permits to discharge pollutants into local rivers, creeks or the bay during at least six of the 12 reporting periods in 2005, according to U.S. PIRG.

Chevron's refinery in Richmond also dumped more mercury and other pollutants into San Pablo Bay than allowed under its permits during half of the reporting periods in 2005.

Chevron spokesman Alex Yelland said the San Ramon-based oil giant is still studying the report's findings but insisted the company is "committed to the highest standards of environmental stewardship."

The report was based on EPA data obtained through the Freedom of Information Act for 2005, the most recent year available. Among the major findings:

-- 3,600 major facilities nationwide - 57 percent of all facilities that must report to EPA - exceeded their Clean Water Act permits at least once in 2005.

-- The average violation was almost four times the legal limit of what can be dumped into waterways.

-- 628 facilities violated their Clean Water Act permits for at least half of the monthly reporting periods, and 85 sites exceeded their permits during every reporting period.

The report's authors said the survey probably underestimates the problem because it looked only at data from major facilities, not smaller sites that also pollute.

Scientists and regional regulators say the water quality has improved in San Francisco Bay and other local waterways because of tougher regulations that followed the passage of the Clean Water Act in 1972.

Jay Davis, lead scientist for the regional monitoring program at the San Francisco Estuary Institute, said those rules have largely solved problems with organic waste and nutrients that have led to algae blooms and oxygen depletion in other bays worldwide. But San Francisco Bay still faces problems with industrial toxins - mercury, PCBs and the chemical in flame retardants, PBDEs - which threaten the health of humans and wildlife.

"The bay is doing pretty well," Davis said, "but there are toxic pollutants entering the bay, some of them coming through wastewater treatment plants, a lot of pollutants coming from sources like urban runoff and atmospheric deposition. A lot of pollutants flow in from the Central Valley through the Sacramento River and the San Joaquin River."

The San Francisco Bay Regional Water Quality Control Board is the key local regulator, leading efforts to limit storm water runoff and nonpoint source pollution. The agency can levy administrative fines and refer cases to state or federal prosecutors. But the EPA is chief enforcer of the law.

With recent budget cuts at EPA, U.S. PIRG's Leavitt complained, "there aren't enough cops on the beat."

Environmentalists are trying to drum up attention about the Clean Water Act, focused on the 35th anniversary of the law. It was passed by a Democratic Congress and signed by Republican President Richard Nixon on Oct. 18, 1972.

While all sides agree that the act has improved water quality across the country, the Bush administration has narrowed the law's reach with new regulations. The law's backers have also clashed with the White House over funding to help communities upgrade their sewage treatment systems.

'The job is still immense'

Rep. James Oberstar, D-Minn., the chairman of the House Transportation and Infrastructure Committee, who attended a Capitol Hill news conference Thursday to release the U.S. PIRG report, said the act has improved most waterways. But he added that one-third of U.S. surface waters don't meet federal water quality standards.

"The job is still immense," Oberstar said.

House Democrats are pushing a bill to strengthen the federal government's ability to regulate U.S. waterways. It's partly a response to the Supreme Court's recent decisions in two wetlands cases that limited the government's authority under the act.

Water agencies and environmentalists are also urging Congress to put more money into the Clean Water State Revolving Loan Fund, which helps states pay for new wastewater facilities, pollution controls and estuary management.

Online resource

To see the full report:

links.sfgate.com/ZBDK

Trouble spots: A list of Northern California sites exceeding federal limits. A13

Online: For a complete list of the California state data, go to: links.sfgate.com/ZBDH

E-mail Zachary Coile at zcoile@sfchronicle.com.