Well, Septic, & Sewer

Rebuilding information related to water wells, septic systems, and sewers in areas affected by the major wildfires within Sonoma County.

On This Page:

• Septic Systems
• Water Wells
• Larkfield-Wikiup (2017 Sonoma Complex Fires)
  • Larkfield Estates Sewer Project
  • OnePave Program for Roadway Trenching
  • Larkfield Estates Holding Tank Option

Permitting Guidelines for Fire Damaged Septic Systems

Find out what type of septic system repair and replacement requires a permit and what type does not require a permit for properties impacted by the major wildfires within Sonoma County.

Septic System Evaluations for Rebuilding and Temporary Housing for Major Wildfires

Permit Sonoma has developed a new form for Professionals to use to document the location and evaluate the condition of septic systems. This form is intended to streamline the findings report creation and review process related to fire rebuilding after the major wildfires within Sonoma County.

Non-Standard Septic System Operational Permit Fees

The County of Sonoma has or will be evaluating properties enrolled in the County’s non-standard septic system operational permit program (OPR Program) to determine if those properties were affected by the major wildfires within Sonoma County. County staff perform field inspections and/or evaluate aerial imagery to determine which properties sustained structural losses that would prohibit the proper use of the property’s non-standard septic system.

Residential Fire Rebuilding Septic System Site Evaluations

In an effort to provide greater customer service and efficiency to the septic permitting process related to fire rebuilding, participation by Permit Sonoma staff in septic site evaluation field work (soil profile evaluations, groundwater determinations, and percolation testing) will not be required for single-lot residential developments on legally existing parcels. Qualified Consultants shall independently perform septic site evaluations related to fire rebuilding septic permits.

Information and forms about the process and procedure:

• WLS-036 Septic System Evaluations for Rebuilding and Temporary Housing (County Declared Disaster)
  To evaluate septic systems on properties impacted by County declared disasters and for properties providing temporary housing connections to existing septic systems with no county records, (authorized by Sonoma County Urgency Ordinances 6210 and 6212). (PDF: 239 kB) (Version 12/01/2019)
• WLS-039 Soil Profile Evaluation Form (County Declared Disaster)
  To determine soil suitability to site and design septic systems. (PDF: 762 kB)
• WLS-040 Soil Percolation Test Data Form (County Declared Disaster)
  To determine soil percolation rates to site and design septic systems. (PDF: 230 kB)
• WLS-041 Wet Weather Ground Water Determination Form (County Declared Disaster)
  To determine presence and depth of groundwater to site and design septic systems. (PDF: 207 kB)
• WLS-045 Septic Site Evaluation General Guidelines (County Declared Disaster)
  To provide guidance for septic site evaluations related to County declared disaster rebuilding efforts. (PDF: 169 kB)

Water Well Recommendations and Requirements After Wildfire Storms (PDF)

As an owner of a private domestic water well that may be damaged by a wildfire, you may have some concerns about fire related impacts to your well and water system. Sonoma County recommends the well owner perform a visual inspection of their well and water system, including the piping and plumbing that provide water to and throughout your home. (PDF: 539 kB)

Larkfield Estates Sewer Project

Connections to the new sewer system require the following permits. All permits must be obtained prior to start of work and final approval of work will be required prior to final occupancy of any related building permit.

• A Sewer Construction permit is required to install a sewer line from the building to the sewer lateral or main line. If any work in the right-of-way is necessary then a separate Encroachment permit is also required. The sewer construction permit authorizes sewer work, such as the installation of pipes and cleanouts, to connect to the sewer system and is subject to Sonoma Water standards. The encroachment permit authorizes work in the right-of-way, such as pavement cuts and restoration, and is subject to DTPW standards and the One Pave program.
• A Septic Tank Destruct permit is required to destruct or remove existing septic tanks and for the abandonment of existing septic systems which is requirement to connect to the new sewer system.
• A Sewer Fee Only permit is required for the assessment and collection of any required connection and service fees. This permit is required to obtain sewer service.

More information regarding Sonoma Water’s Larkfield Estates Sewer project.

OnePave Program for Roadway Trenching

The county has adopted a OnePave Program intended to provide better-quality, longer lasting roads and facilitate rebuilding efforts specific to the fire damaged areas of Larkfield-Wikiup where a high concentration of utility and other infrastructure work for individual rebuilding projects is anticipated to result in extensive trenching in the area’s roadways.

Larkfield Estates Holding Tank Option

View the Larkfield Estates Subdivision Zone Map

Due to the unprecedented fires that devastated our community in October 2017, Larkfield Estates property owners are challenged with rebuilding, including the best way to manage wastewater. Lots in the subdivision have varying types of septic systems. Many of the properties have serviceable septic systems that can accommodate reconstruction. Other parcels have systems that could support redevelopment but not to the scale at which owners are allowed to rebuild under existing zoning regulations. Some sites have failed systems that need to be replaced.

To provide another option to fire survivors, the Sonoma County Water Agency will consider extension of sewer service to the subdivision. For those owners who wish to connect their properties to the sewer main (which, if approved, will take at least a year to authorize and construct) and proceed with reconstruction, Permit Sonoma would allow the use of holding tanks as an interim measure. Properties with compliant septic systems will not be compelled to connect to new main.

In providing this option Permit Sonoma does not take a position on whether owners should connect their properties to the sewer system, if approved and constructed. The agency takes this action regarding holding tanks to provide another option for fire survivors trying to rebuild on or sell their properties.

Regulations allow the use of holding tanks under certain conditions. Sonoma County Code Section 713.9 provides, “No privy [holding tank], including vault privies, chemical privies, pit privies or cesspools shall be constructed, maintained or used except upon written approval of the Director of the Permit and Resource Management Department (Permit Sonoma) unless otherwise specifically permitted by law.” The Regional Water Quality Control Board Basin Plan provides for the use of holding tanks if the proposed use is in a sewer service area, sewer service extension is underway and will be completed in two years, and the treatment plant has capacity to meet the proposed users’ needs.

Permit Sonoma will track the use of holding tanks through building permit applications. No additional permits will be required. For the best use of holding tanks, please visit or contact the Resiliency Permit Center at: