The ambitious project approved this week by county supervisors is aimed at cutting by 20 percent the amount of pollution generated by its operations by 2010, emissions produced by everything from its 4,300 employees commuting to work to its crews repairing highways. The plan stops just short of forcing government workers to pay for parking, although supervisors said that will be considered if incentives don't work.

"I am convinced people want to do the right thing if people know what's the impact on the environment," Supervisor Tim Smith said.

The county's greenhouse gas reduction program puts some substance into a pledge signed last year by county government and all of Sonoma's nine cities to cut emissions. The pledge was the work of local activists with the Climate Protection Campaign who are prodding public agencies and private companies to take measures against global warming.

Ann Hancock, Climate Protection Campaign coordinator, said Sebastopol was first to adopt an emission reduction plan last week. Earlier this year, students at west county's Analy High School were working to reduce solo driving to classes.

"If we can do (a program to cut car trips) aimed at the adult population, then other cities can be inspired," Hancock said.

Dave Kronberg, the county's general services director, said a survey found that 90 percent of county workers drive to work alone, only 184 workers use bus passes and 16 people car pool.

Employees commuting to work account for about 38 percent of the 37,000 tons of gas emissions produced by county government annually, the study also found. The study estimated that 543 employees, or nearly 13 percent of the work force, would have to abandon solo driving for the county to reach its goal.

Incentives for commuters likely will center on free or discounted bus passes, telecommuting, flexible work schedules and special parking spots for car poolers, Kronberg said.

County Administrator Bob Deis said more drastic efforts may be necessary.

"There are difficulties because it requires about 500 employees to change their commute patterns," Deis said. If goals aren't achieved, he added, "we may be going to the disincentive side"

Kronberg estimated the county will spend about $4million to reduce emissions with measures that include converting construction equipment to biodiesel and replacing its fleet of vehicles. Currently, the county has 57 hybrid cars for use by employees; 243 gasoline-powered vehicles would have to be jettisoned before the entire fleet operates on gas and stored electricity.

Other measures include conversion of methane gas produced at the county landfill to electricity and application for state and federal grants for rooftop solar panels on county buildings.