Subject:   Individual sewage disposal system guidelines for the remodeling, addition and/or change in use to an existing structure.

References:
Marin County Code, Chapter 18.06,
Marin County Regulations for Design, Construction and Repair of Individual Sewage Disposal Systems
Uniform Plumbing Code

Background:
These guidelines establish criteria to be followed for projects involving the remodel, addition, and/or change in use of a residential or commercial structure. It is the intent of these guidelines to further define the extent of a remodel, addition and/or change in use that can be accommodated when the individual sewage disposal system is not currently or cannot be constructed in full compliance with the Marin County Code.

Statement of Purpose:
It is the intent of the Marin County community Development Agency (CDA), Division of Environmental Health Services, to provide the highest level of public health protection while, at the same time, accommodate the public's need for modifying existing structures and uses. The policy below is meant to provide uniform and consistent guidelines for environmental Health Services staff and the public to follow when considering a remodel, addition and/or change in use to an existing structure or property.

Policy:
The criteria established below shall be followed in the consideration of all applications. In the case where the appropriate criteria cannot be specifically determined, conditions may be attached to the project as specified in Section V.

Section I

Criteria
The following provisions set forth individual sewage disposal system requirements by system class based on the extent of proposed remodel, addition or change in use to an existing structure or property. (Note: If the subject property is within 400 feet of a public sewer, modifications to an individual sewage disposal system may not be permitted pursuant to Section 18.06.050 of the Marin County Code).

A.  Status of Individual Sewage Disposal System Definitions

• Class I:
  The individual sewage disposal system is in compliance with current Marin County Regulations for Design, Construction and Repair of Individual Sewage Disposal Systems (Standard Systems or Alternative Systems, Category 2 or 3 may apply).
• Class II:
  The individual sewage disposal system complies with the requirements established for Repair of Existing Systems (Marin County Regulations for Design, Construction and Repair of Individual Sewage Disposal Systems, Section 304).
• Class III:
  The individual sewage disposal system has been permitted by the Health Officer pursuant to Chapters 18.04 or 18.06 of the Marin County Code. In addition, a performance evaluation report has been prepared by a qualified professional who has determined that the system is in good working condition and does not pose a threat to water quality or public health. The evaluation report must include, at a minimum, a site plan which delineates the location of the individual sewage disposal system, all structures located on the property, nearby geologic features, such as, cutbanks and creeks, water wells, reserve area, property slope, projected water use data, projected wastewater strength, and any other item determined to be necessary by the Health Officer in order to adequately evaluate the system. If the leachfield is not a dual 100% system or does not have a dedicated reserve or fail-safe area, an adequate reserve area must be located and sited.
• Class IV:
  Cesspools (as defined pursuant to Section 104(b) of the Uniform Plumbing Code, 1991 Edition) or other systems for which no documented records are available.

B.  Discussion

The satisfactory performance of a Class I and Class II individual sewage disposal system must be substantiated by qualified professionals, usually either a registered civil engineer or registered environmental health specialist. Inspection and/or verification by Marin County Environmental Health Services staff may be required. Individual sewage disposal system performance inspection procedures are shown in Attachment A. Waivers in siting and design may be approved for Class I systems provided technical merit is submitted, substantiated and approved by Environmental Health Services. No waivers will be allowed for reductions in setback to groundwater, surface water, or adjacent wells, the requirements for dual 100% leach fields or fail safe area, or when the Health Officer finds that a threat to water quality or public health could result. For Class II systems, waivers, to either Standard System design and siting criteria or Alternative System design and siting criteria (Category 1, 2 or 3) may be approved, provided the Health Officer determines that a threat to water quality or public health would not result. A Class IV system may be approved for any required safety and/or structural improvements to a structure provided the Health Officer determines that the cesspool poses no threat to water quality or public health.

Section II

Residential remodel, addition and/or change in use

Proposed Extent of Remodel and/or Addition:

1. Addition of New Bedrooms: An adequately sized Class I system is required.

   Note:   For the purposes of determining number of bedrooms or the minimum number of bedrooms based on the square footage of the residence, Section 204 of the Marin County Regulations for Design, Construction and Repair of Individual Sewage Disposal Systems shall be used.

2. Addition Other than bedrooms

   Addition:

   Increase (SF)	Minimum Class Required
   0 - 20%	III
   21% - 39%	II
   40% and over	I

3. Remodel of Existing Habitable Space:

   
   

   (SF)*	Minimum Class Required
   0 - 20 %	III
   21% - 39%	II
   40% and over	I

   Note:
   *The above percentages are in reference to the square footage (SF) based on the original permit for the structure.

4. No remodel and/or addition project will be permitted with a Class IV system.

5. For a project proposing both a partial remodel of a building and an addition to the same building, the combined total of both areas shall be used to determine the required class of system.

6. Detached accessory structures which do not propose bedrooms and/or additions of habitable space (i.e., garage, workshop, storage building, swimming pool, barn) to an existing structure:

• Class I, II or III system may be permitted provided that the individual sewage disposal system is found to be in good working condition and not pose a threat to water quality or public health. Satisfactory performance of the system must be demonstrated prior to approval of the accessory structure. An individual sewage disposal system evaluation report prepared by a registered civil engineer or registered environmental health specialist shall be submitted to Environmental Health Services. Inspection and/or verification of the above may be required by Environmental Health Services staff. All required setbacks must be maintained and encroachment upon or usurpation of a required fail-safe or reserve area is not permitted.

Section III

Commercial addition, remodel with no change in use

1. Remodeling which does not involve structural changes in floor area, height, bulk or mass and does not add to the loading of the individual sewage disposal system or strength of the wastewater may be approved provided the system is evaluated by a qualified professional and found to be in good working condition pursuant to a submitted  evaluation report, and pose no threat to water quality or public health. Inspection and/or verification of the above may be required by Environmental Health Services staff.
   System Class:  Septic systems may be Class I, II or III.
2. Addition to Existing Commercial Space:

3. Remodel of Existing Commercial Space:

4. For a project proposing both a partial remodel of a building and an addition to the same building, the combined total of both areas shall be used to determine the required class of system.

5. No remodel and/or addition project will be permitted with a Class IV system.

Section IV

Commercial Addition, Remodel With Change in Use.

If the project has the potential for increasing sewage loading and/or sewage strength based on review of an engineering report and subsequent determination by the Health Officer, a Class I system will be required.

Section V

Conditions of project approval

In addition to the conditions set forth above, the Health Officer may apply conditions of approval to a proposed project in order to ensure protection of water quality and public health. Such conditions may include, but not be limited to the following:

• Conditional sewage disposal permit.
• Deed restriction.
• Operational Permit for the individual sewage disposal permit.
• Any combination of the above or other conditions as determined to be necessary by the Health Officer.

Section VI

Appeal Process

Any person who disagrees with the decisions or subsequent actions made under this policy can appeal such decision or action rendered as a result of this policy pursuant to Marin County Code, Section 18.06.140.

Effective Date

This policy will be effective Feb. 1, 1996 and will remain in effect until canceled or superseded.
Ed Stewart
Chief, Environmental Health Services