Groundwater Monitoring for Septic Systems

Percolation systems can only work in soils above the level at which it is saturated with groundwater, and San Diego’s Department of Environmental Health (DEH) safeguards this resource with a requirement for minimal vertical distance through which wastewater must pass on its way to groundwater. As of this writing, late 2021, southern California remains in years-long drought. These times depress the groundwater level and will make county approvals difficult for many areas, where high groundwater was known to be a limiting issue.

Wet times are bound to return eventually, and for some areas, a deep dry exploratory hole is not evidence enough that groundwater won’t again be a problem. For these areas testing and design cannot readily proceed without further resolution, which is only met by waiting until wet-times and then measuring groundwater depth then.

It can’t be known when a really wet season will come, so many projects would be on an indefinite hold. Fortunately, an alternative approach usually exists, that of near-surface release of effluent from a Supplementary Treatment System (STS). Treated water from an STS may percolate in soil as shallow as 6-inches, allowing greater separation from high groundwater and county approval despite lack of groundwater monitoring.