A Standard Septic System is a conventional onsite sewage disposal system which consists of a septic tank and leach field, which meet the current standards for tank size, leach field size, groundwater separation, setbacks from streams, cut banks, etc. The required size of the leach field for a residence is determined by the number of bedrooms and the soil type. There must also be adequate "expansion area" on the parcel to accommodate a standard replacement leach field which can be installed when the existing leach field fails. Under current standards, which have been in place since 1995, at least 90% of the 400 septic system repairs in the San Lorenzo River Watershed have met requirements for a Standard System. Parcels with Standard Systems are eligible for major building additions, provided standards can still be met after the remodel. (See specific standards in County Code Chapter 7.38 and in the Standards and Procedures for the Repair and Upgrade of Septic Systems.)
A Non-Standard System is a recently permitted septic system (since 1993) which either uses alternative technology or does not meet critical requirements for a standard conventional septic system, such as groundwater separation, leach field size, or availability of expansion area. Parcels with septic systems that do not meet standards are eligible for only minor building additions (a one-time addition of less than 500 square feet and no bedroom additions). Parcels with alternative systems such as mound systems, at-grade systems, sand filters, or treatment units may be eligible for major building additions.
Because most Non-Standard Systems require special operating conditions (such as water conservation or regular pumping) and additional maintenance and oversight to ensure they function properly, County staff inspect them on an annual basis and charge an annual fee on the tax bill of those systems that require inspection. (Annual fees are collected through CSA 12.) Prior to approval and installation of a Nonstandard System, the property owner signs an Acknowledgment of Nonstandard System which indicates that they recognize and accept the special operating conditions and limitations required for use of such a system.