ONSITE WASTEWATER MANAGEMENT PROGRAM
HOMEOWNER'S GUIDE

BUILDING, REMODELING OR ENLARGING YOUR HOME

If your parcel is within the jurisdiction of the Stinson Beach County Water District (SBCWD), the Application for Building Permit must be reviewed and endorsed by District staff. Please review the following to avoid unnecessary delays to your project.

Prior to release of the Application for Building Permit, the following requirements must be met:

New single family residence or commercial facility:
The property owner must obtain a construction and discharge permit for an onsite system from the Stinson Beach County Water District. Contact the District for the appropriate forms and fee schedule.

Building additions which add square footage to the conditioned space of a pre- existing structure:
The District defines this a new construction (see definition below) and requires that the onsite wastewater disposal system meet current District Code (SBCWD Ordinance WW2000-01). Variances to this provision can be applied for if the current system is an engineered system, is in excellent operating condition, and if the residence will not exceed the square footage limitations defined by the size of the current system. The variance procedure is outlined in Chapter 4.13 and requires San Francisco Regional Water Quality Control Board review and SBCWD Board approval. If a variance is granted, the applicant must demonstrate that the system is functioning as designed.

4.03.252 New Construction. "New construction" shall mean the construction of a new building, or the construction of an addition to, the alteration of, or the remodeling of an existing building which results in an increase in habitable space or other heated or otherwise conditioned space within the building. Further, the construction of any new structure within a setback from a component of a wastewater disposal system required at the time the system was installed shall be deemed to be "new construction."

Building remodels that either do not add square footage to the conditioned space of a pre-existing structure or involve accessory structures such as - garage, workshop, storage buildings:
The District defines this as alterations and additions that do not constitute new construction (see definition below) and requires that the septic system must be found to be adequate for the residence, to be in good working condition, and not jeopardize public health or safety. An evaluation of the onsite wastewater disposal system will be required. This evaluation must be conducted by a qualified professional, usually a civil engineer or registered environmental health specialist.

4.01.410 Alterations and Additions to Buildings. Whenever any person makes application to the County of Marin for a building permit for the purpose of making any alterations to, or enlargement of any structure which meets the definition of "New Construction" as set forth in 4.03.252, said applicant must demonstrate that the existing septic system meets the requirement set forth in this Code.
An applicant may be exempt from this requirement if s/he can demonstrate that there is currently a septic on the subject property that substantially complies with this code, that is:

1. An engineered gravity flow system in an area of appropriate percolation rate and ground water depth for such a system; or
2. A sand filtration system that incorporates timed dosing and provides a means to purge all laterals.

Determination of whether or not a system substantially complies with this code is within the joint discretion of the District Engineer and the General Manager.