Revised state rules regulating septic tanks would more narrowly target landowners with systems that are failing or are near polluted waterways, lakes, bays or ponds.
Such rural property owners could be on the hook for mandated testing and upgrades costing tens of thousands of dollars under the proposed rules, which state water officials released last week.
The move could rekindle protests from rural landowners and property rights activists, who packed local hearings on the issue in 2009 and helped beat back a set of rules they considered heavy-handed.
Most of the leading critics at that time said Tuesday they were still studying the latest proposal and were not prepared to comment. Others could not be reached.
A public meeting with afternoon and evening sessions will be held on the issue Nov. 2 at the Wells Fargo Center in Santa Rosa.
State water officials acknowledged that heated opposition two years ago sent them back to the drawing board. The initial plan would have affected nearly all the 45,000 septic tank owners in Sonoma County at the time, requiring regular system tests and retrofits of up to $45,000 for a wider range of residential properties.
"The approach we had was pulling in too many folks, adding in properties and costs that were unnecessary," said Jonathan Bishop, chief deputy director of the state Water Resources Control Board.
The agency is now in its third attempt to craft rules that would meet a 2000 state mandate to crack down on water quality problems caused by septic systems.
Officials said the new proposal, with tiered regulations for different situations, is designed to achieve that goal without affecting most of the 1.3 million California property owners statewide who use septic tanks instead of municipal or district sewer systems.
About 50,000 of those septic owners are in Sonoma County. Most would not be subject to additional requirements or costs under the new rules, state officials said.
The tightest oversight would be reserved for landowners near streams and other water bodies with high bacteria and nitrate levels.
In the North Bay, that includes landowners who have septic systems within 600 feet of "impaired" stretches of the Russian River, Petaluma River, Laguna de Santa Rosa, Santa Rosa Creek and Sonoma Creek.
Those landowners would be required to test for groundwater pollution and make retrofits if problems are discovered. Total costs, including $5,000 for testing, could add up to $27,000 or more for a three-bedroom home needing a new system, state estimates showed. Costs for a typical restaurant or school were seven to 25 times higher, respectively, state studies showed.
How many landowners would be subject to such requirements is unknown, state officials said. A program on the state water board's website allows property owners to plug in their addresses to determine if they are within the riparian zones.
The rules could result in another standoff with critics of state regulation, said Sonoma County Supervisor Valerie Brown.
Brown recalled the anger over the previous rules and noted that she could be among those subject to the new rules. The only supervisor with a home in unincorporated Sonoma County, Brown lives just south of Kenwood in a home with a well and septic system near Sonoma Creek.