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.