State regulators Tuesday adopted new rules designed to fix failing septic systems, including those that may be polluting California waterways.
The rules were scaled back from a 2009 proposal that drew heavy criticism.
Those scrapped rules would have affected nearly all 45,000 septic tank owners in Sonoma County, requiring regular system tests and retrofits of up to $45,000 for a wide range of residential properties.
The new proposal would more narrowly focus the strongest regulations on landowners with systems that are failing or are near polluted rivers, lakes, bays or ponds.
In the North Bay, that latter group 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.
Regional water boards have two to five years to study where pollution is coming from, what role septic systems play and determine how to fix failed systems and regulate systems for new homes.
Individual property owners would be required to retrofit or replace systems where problems are discovered. The cost could be as much as $27,000 for improvements to a system serving a three-bedroom home.
The regulations were adopted by the state Water Resources Control Board. They were designed to meet a 2000 state mandate by the legislature to crack down on water quality problems caused by septic systems.
The new rules start to take effect in February. State officials said they anticipate that about 2 percent of the 1.2 million septic systems statewide will be affected.
Landowners near waterways can enter their address into a web-based mapping tool to see if they may be affected by the new policy.