Septic Disposal In San Diego County
San Diego County has three types of onsite disposal systems approved for new construction and subdivision of land. (An exception is the use of “Mound Systems” in the former moratorium areas of the central Valley Center basin and also the South Citrus Avenue area of Escondido).
Vertical Seepage Pits are limited to a defined area along the coast and the inland basins of Rancho Santa Fe and the Bonita Valley. The qualifying constructs for their use includes degraded groundwater to at least 1500 mg./L “TDS”, homogeneous sedimentary soil and within the boundaries of a regional map provided by the Regional Water Quality Control Board(borderline properties can be argued on merit if they meet the TDS and sedimentary soil constructs).
Horizontal Seepage Pits are approved if the soil can be certified with no percolation rates in excess of thirty minutes per inch. Technically, the soil must be homogeneous throughout sidewalls of the pit length. This is rare because the density of soil from highly weathered granitic rocks (sandy decomposed granite) tends to vary greatly. Adequate testing throughout the length and depth of the pit in association with observed drilling of deep borings is necessary to obtain information for a judgment and recommendation.
Leach Fields are the most frequent type of subsurface installation because they have the advantage of adjustment for contours, slope and soil depth. They also cost less to install. The type of leach field in San Diego County is often described as a “serial system” because each leach line functions as a separate cell before overflowing via a siphon to the next leach line in a series. These systems have a very good record of function when correctly installed and in soil which has a percolation rate appropriate for the hydraulic loading. (This is sometimes referenced to a “long term acceptance rate” and is essentially a measure of how much soil area is necessary to accept a given volume of septic effluent during a specific time).
A History of Percolation Testing
Percolation testing as defined for the purpose of sizing a leach field
Changes in San Diego County Regulation over the years