The purpose of regulating the design, installation, and maintenance of septic systems (onsite wastewater treatment systems) is to prevent public health nuisance conditions caused by failing onsite wastewater treatment systems. The program's goals are:
- Ensure that these systems can operate in all weather conditions with minimal maintenance
- Prevent the contamination of groundwater from improperly designed onsite wastewater treatment systems
- Prevent the contamination of surface water from improperly designed onsite wastewater treatment systems
- Prevent premature failure of onsite wastewater treatment systems
- Design review of new onsite wastewater treatment systems and Graywater Systems
- Design review of repairs and modifications to existing on-site wastewater treatment systems
- Installation inspections of onsite wastewater treatment systems
- Maintain design records for properties using onsite wastewater treatment systems
- Respond to citizen complaints of failing onsite wastewater treatment systems
- Provide coordinated review with other agencies for projects that require CEQA (California Environmental Quality Act) and involve the use of onsite wastewater treatment systems
Currently DEH is approving conventional system and supplemental treatment systems:
- Septic tanks must have IAPMO approval and be approved for use by DEH.
- Leach lines can be constructed with either rock and pipe or other approved materials that would include plastic chambers
- Horizontal seepage pits are restricted to sites with uniform soil conditions and average percolation rates not exceeding 30 minutes per inch.
- Vertical seepage pits are restricted to coastal sedimentary basins that have degraded groundwater caused by salt water intrusion.
- Mound systems are allowed in the areas within the former Valley Center Moratorium area where engineering demonstrates the site conditions are suitable.
- Supplemental treatment systems must include percolation testing and a design from a licensed OWTS Professional.
- Any site with slopes that exceed 25% must include with the layout a slope stability report or statement from a licensed civil engineer or geologist.