The Federal Emergency Management Agency (FEMA) published new Flood Insurance Rate Maps for the Russian River Watershed on July 31, 2024, and these were adopted by the County of Sonoma on Jan. 14, 2025. Based on the updated FEMA map, parcels that are within the 100-year flood area are required to have backflow prevention devices installed to prevent untreated sewage from entering the main water supply.

This requirement is part of the Design and Construction Standards for Sanitation Facilities and is also included in each sanitation district code ordinance.

DESIGN AND CONSTRUCTION STANDARDS FOR SANITATION FACILITIES

2.8 Maintenance of Backflow Prevention Devices

Side sewers within the reach of the connecting main sewer and serving plumbing fixtures located 1) less than one (1) foot above the rim elevation of the nearest upstream manhole or main sewer cleanout, or 2) within the 100-year flood zone shall be protected from backflow of sewage by installing a backflow prevention device in the building sewer in accordance with Agency Standard Drawing 127. The backflow prevention device shall be located on private property and shall be installed by the Permittee. The maintenance of the backflow prevention device shall be the sole obligation of the Permittee or Permittee's successor in interest. The Agency shall be under no obligation to ascertain that the backflow device continues in operating condition. The installation of a backflow prevention device shall require a permit from, and shall require inspection by, PRMD (Permit Sonoma).

Homeowners can determine if their property lies within the 100-year flood area by using the FEMA Flood Hazard & Zoning Update (F1 & F2) Map and entering their address.