More than $2.7 billion is needed to repair crumbling pavement on county roads and city streets over the next decade in Sonoma, Mendocino and Lake counties, a new report has found.

Overall road conditions in the three counties are among the worst in the state, the survey showed. The average score for Sonoma County puts it at the bottom of a group that includes most counties in the state where roads are said to be "at risk" of long-term failure.

Mendocino and Lake counties are ranked even lower, grouped among seven counties statewide with overall "poor" conditions in need of more immediate and expensive upgrades.

The findings are contained in a new report released Tuesday by groups representing California counties, cities and transportation agencies and interests.

The latest survey follows on similar reports issued in 2008 and 2010. The 2012 edition pegs the 10-year maintenance backlog for county roads and city streets statewide at $72.4 billion, up 2.7 percent from two years ago.

For Sonoma County, including city streets, the needed repairs amount to $1.6 billion. A separate Sonoma County estimate not included in the statewide report put maintenance needs on unincorporated roads over the next 10 years at $920 million.

The repair total countywide in Mendocino is $617 million; for Lake County it is $450 million.

Statewide, long-range repairs to local bridges and street infrastructure, including sidewalks and storm drains, push the total 10-year repair backlog to $107.2 billion, according to the report.

But with only $25.1 billion in anticipated long-range funding, local governments are facing a combined $82.4 billion shortfall between now and 2022, up 4.8 percent from two years ago, the survey found.

The new shortfall is the equivalent of a 56-cent per gallon gas tax increase, or an additional 76 cents a day for the average California driver, survey authors said.

While not advocating for any particular tax increase, the report concludes that without additional money, repair costs will soar and "California's local streets and roads will continue to deteriorate rapidly within the next 10 years."

The report is part of a stronger push by local governments for additional state and federal road funds to turn the situation around.

Sacramento currently supplies about 59 percent of funds for pavement work, mainly through gas taxes. Federal funds kick in about 10 percent and local governments supply about 31 percent.

The report is largely silent on what could be biggest revenue generator: an increase in the state gas tax, which hasn't been changed in over two decades.

It also did not address a request by Sonoma County and other rural counties to revisit distribution formulas that favor urban counties with smaller road networks.

Sonoma County road advocates said they saw little new or groundbreaking in the study.

"It is unfortunate that the report seems unable to advocate solutions," said Craig Harrison, cofounder of Save Our Sonoma Roads, a group that's lobbied for increased county spending on roads.

Sonoma County officials are considering several kinds of tax increases. Road advocates have acknowledged some form of tax increase may be necessary while they solicit ideas.

"Our road system is failing and if we don't do something about it locally, nothing will change," Harrison said.

The report did show that most California counties are faced with road repair backlogs.

Including Sonoma, 44 counties in California have local road systems that are at long-term risk of failure due to deteriorating pavement conditions and other delayed upkeep.

Seven counties, including Mendocino and Lake, are seen as worse off. Their overall "poor" pavement conditions could degrade faster and require more costly repairs, the report found.

The seven counties given a "good" road condition score were Sierra, Nevada, Placer, Contra Costa, Santa Clara, San Mateo and Orange, which had the highest ranking for pavement condition.

California counties and cities own and maintain 81 percent of the state's public roads, a network valued at $189 billion.

The overall condition of the network has not changed since 2010. On a scale of zero (failed) to 100 (excellent), the average score statewide remains at 66.

But just to maintain that statewide average would require a nearly 150 percent increase in annual funding, from the current $1.3 billion to $3.2 billion, according to the report.

Providing that money sooner could significantly decrease future costs, the report concluded.

The report was sponsored by the California League of Cities, the California State Association of Counties, the Metropolitan Transportation Commission and other transportation interests.

You can reach Staff Writer Brett Wilkison at 521-5295 or brett.wilkison@pressdemocrat.com.