The move to ban plastic carry-out bags in Sonoma County could take a major step forward on Wednesday when the county's waste management agency considers conducting an environmental impact assessment.

If the board of the Sonoma County Waste Management Agency approves the impact report, it would signal support by all cities and the county for a countywide ban, said agency spokesman Patrick Carter.

"If they say go forward, it is the first time all 10 jurisdictions will say that we are all in agreement and want to move forward," Carter said.

The agency is considering an ordinance modeled after what already has been adopted in other jurisdictions banning carry-out plastic bags at check-out stands and placing a 10-cent fee on paper bags.

It also sets up an administrative process that could fine violators $100 for a first offense, $200 for a second violation and $500 for a third.

The intent is to shift consumers to reusable bags to reduce litter, conserve space in landfills and address other environmental impacts. An estimated 300 million plastic and paper bags are used in Sonoma County every year.

Under the agency's policy, the ordinance can only be adopted by a unanimous vote of the 10-member board, which is made up of representatives of each of the nine cities and Sonoma County.

Once adopted, a ban could take effect in Sonoma County and all of its cities without any further action by the cities.

The board Wednesday is being asked to authorize seeking requests from consultants to conduct the environmental impact analysis, at an estimated cost of $80,000 to $150,000.

It would signify that each of the cities and the county agree with the requirements that are in the draft ordinance, Carter said.

Bans have been enacted in many California counties, including Mendocino, Marin, Alameda and Santa Clara, and in 35 cities, including San Francisco and San Jose.

The Sonoma County agency is funded by a surcharge of $5.95 a ton assessed at the county's landfills.

The board is meeting at 9 a.m. in the City of Cotati Community Room.