DIRECTOR BULLETIN No. 1: ADU Legalization and Septic Review

This bulletin establishes the internal framework for Environmental Health Services (EHS) review of on-site wastewater treatment systems (septic systems) associated with Planning Entitlements and Building Permits when a property owner is seeking the legalization of existing Accessory Dwelling Units (ADUs).  

This bulletin applies only where the permit application is strictly for legalization of an existing ADU pursuant to the provisions of the Government Code sections 66314-66331.  Qualifying applications may include maintenance and repairs, but no remodeling, expansion, or structural modification.  This bulletin does not affect or amend the process applicable to other development applications.  In addition, this bulletin applies to the County’s internal process alone, and does not create any rights for third parties such as project applicants.  

The intent is to encourage property owners to submit appropriate building permit applications, thereby promoting safe and healthy built environments, while maintaining a balanced public health approach that applies proportional regulatory requirements when existing systems are confirmed to be functioning adequately.  

This bulletin applies when:  

• The permit request is for legalization only and applies to existing attached or detached ADU’s.
• No additional expansion or structural modification is proposed.  No interior remodeling of the primary unit is proposed.
• Projects that constitute typical maintenance and repair activities such as re-roofing, installing new windows, making energy efficiency improvements, plumbing permits, electrical permits, new siding, etc. are considered maintenance and repairs and do not constitute remodeling.
• https://www.marincounty.gov/departments/cda/env-health-svcs/prgm-septic The septic system's adequate operation has been verified by a passing septic inspection report. This report must be completed by a qualified professional or approved septic contractor from the Environmental Health Services (EHS) list of approved professionals and submitted within one year of the building permit application. 

If any remodeling, expansion, or structural modification is proposed, this bulletin does not apply, and full compliance with applicable codes and with the 2016 “Remodels & Additions Policy” (2016 Remodel Policy) or other applicable adopted policies will be required.  

Legalization with no physical changes will not trigger the 2016 Remodel Policy.  This means that, where the criteria in this bulletin are met, legalization of the ADU will not require septic system upgrades or modifications.  

Adequate functioning of the system, as determined by an inspection completed by a professional included on the list of qualified professionals and contractors will be required.  The inspection must be recorded on the standard EHS Residential On-Site Sewage Disposal System Inspection Form (Inspection Form).  “Adequate” functioning is defined for the purpose of this Director’s Bulletin as follows: 

• No signs of system failure.  As described on the Inspection Form, this includes but is not limited to odors, sounding alarms, surfacing effluent, backed-up plumbing, evidence of groundwater or surface water degradation, and obvious recent construction in the vicinity of the septic system.
• Septic tank is constructed of approved material and has watertight lids  A tank made of unapproved material or a cesspool does not qualify as an adequately functioning system.
• The results of the Hydraulic Load Test and Dye Test are at a level of “Satisfactory” or better.
• The leachfield shows no overt signs of failure or questionable appearance, as recorded in the “Leachfield” section of the Inspection Report. 

The inspection may conclude that maintenance or repairs to a system are needed or advisable.  If the system has not failed and repairs are recommended, under the discretion provided in the “Regulations for Design, Construction and Repair of Individual Sewage Disposal Systems” these repairs will not themselves trigger a requirement for the system to meet applicable regulations.  

1. Process 

For all Planning Entitlements and Building Permits involving ADU legalization:  

• Verification of eligibility under the Applicability section is required.
• System adequacy must be confirmed by a qualified septic inspector listed on the EHS list of qualified professionals.
• A septic system inspection shall be required prior to permit issuance. This must be completed by a septic inspector listed on EHS Qualified Professionals list, using the standard EHS form.  The inspection must confirm that the system is operating adequately, as described in “Approach” above.
• Should the inspection report not indicate that the system is operating adequately, the property owner must take appropriate steps to bring the septic system up to the necessary level of functioning. Those repairs will not trigger requirements that the system be upgraded to meet applicable regulations.
• This report and the site plan will be transmitted to Environmental Health Services where it will be retained in the property records.
• CDA staff will ensure required ADU approval language described below is included in the permit and is clearly visible in the documentation.
• An ADU using a well or spring will be required to have a domestic water supply permit. 

2. ADU Approval Documentation  

The ADU approval documentation shall include the following:  

1. Information regarding the status of the septic system, including whether it is permitted, the number of bedrooms or other indication of use intensity specified in the permit (if applicable), and any other relevant, known information regarding the septic system.
2. A copy of the septic inspection report and site plan
3. A statement that the ADU approval does not imply authorization of the septic system.
4. A statement that the septic system must be brought into compliance with all applicable codes in effect at the time of application as a requirement for any future major remodeling, expansion, structural modification, or septic system replacement due to failure.
5. A recommendation that low flow fixtures be used throughout the property to extend the lifespan of the septic system.
6. A recommendation for ongoing inspection when the system is unpermitted or exceeds the applicable age threshold, to avoid septic system failure that will require system replacement, and a statement that any future repair needs identified as a result of such inspection will not automatically trigger a full system upgrade to meet regulations.  

3. Ongoing Inspection Recommendation  

For septic systems more than 25 years old or for unpermitted systems, the County will recommend biannual (every two years) septic system inspections so that the property owner can ensure that the system remains functional.  The ADU approval will include a notation that if inspections identify deficiencies, the necessary repairs alone will not trigger a full system upgrade, provided no remodeling, expansion, or structural modification of the property is proposed.  

Inquiries regarding this bulletin should be directed to the Permit Ombudsperson's email, (415) 473-7875.