Land Use Program Septic System Overview Scott Weldon

Definition of “Septic System”  A subsurface sewage disposal system which uses a combination of a septic tank and a effluent dispersal mechanism.  A two-chamber septic tank is used to accumulate solid matter. The solid matter is decomposed by anaerobic bacteria. Clear effluent then passes to the dispersal mechanism, which may be leachlines or seepage pits.  Septic tanks need to be pumped at least once every four years to remove solids.

Septic Systems are required for plumbed structures anywhere there is no public sewer  If public sewer is not within 200’ of a vacant lot that is proposed to be built out, the owner will need to install a septic system that is permitted and inspected by the County of San Diego, Department of Environmental Health.  The intent of a properly designed septic system is to keep sewage underground for at least 25 years.

Map of San Diego County

Percolation tests for septic systems  Consists of at least four 6” diameter borings in the proposed leachline/ pit area.  Must be completed by a licensed professional, and must follow County Policy for percolation test procedures.  A deep boring is also required to verify adequate soil depth and adequate separation to groundwater. Deep borings are 15’-20’ deep. Percolation tests must be completed to determine soil permeability.

Soil Permeability  Soil must be able to accept water over time in order for a septic system to work properly.  Clay soils have poor percolation rates, and may not support a septic system.

Groundwater Protection requirements  5’ separation required from leachlines to groundwater.  10’ separation required from Horizontal or Vertical Seepage Pits to groundwater.  100’ setback required from any portion of a septic system to a water well.  100’ setback required from a septic system to a year-around stream  50’ setback required from a septic system to a seasonal stream.  ¼ mile setback required from a vertical seepage pit to any well

Permit Process. A percolation test or septic layout is submitted and is field reviewed by DEH staff. Project is either approved or disapproved. If it’s disapproved, the owner has 12 months to correct any issues / concerns. 1. A percolation test or septic layout is submitted and is field reviewed by DEH staff. Project is either approved or disapproved. If it’s disapproved, the owner has 12 months to correct any issues / concerns. 2. Grading must be completed prior to issuance of the septic permit (i.e. pad or driveway grading). 3. A septic permit is then issued in order to install the system. The permit is valid for one year, and the system is inspected by the County at the time of installation.

Types of dispersal mechanisms  Leachlines – trenches 3’– 5’ deep with 1-2” rock under and around 4” perforated pipe.  Vertical Seepage Pits – 4’ diameter rock-filled pits. The bottom of the pit is kept at least 10’ above groundwater. Vertical pits are only allowed in areas with poor quality groundwater (basically along the coastline where salt water intrusion has occurred).  Horizontal Seepage Pits – A series of 5’ diameter rings that are 6’ tall. Soil must be very permeable (perc rate < 30 min per inch).

Surface discharge requirements  All sewage effluent is to remain underground. If a septic system fails, the septic tank should be pumped as necessary to keep sewage underground until repairs can be made.  A repair to a failing system usually consists of a 200’- 300’ leachline addition to the existing leachfield.  County Code requires a failing system to be repaired within 30 days.

Surface Discharge Requirements (continued)  Sediment control is important during the rainy season.  When excavating on your property, all run- off/sediment is to be kept on your property by using sediment basins, berms and/or silt fences.

Reserve Requirement  Each lot in San Diego County that has a septic system on it must have a designated area to replace the dispersal field should it fail. This area is known as the “reserve area”. No structures or hardscape may be placed in this area.  The average life expectancy of a septic system is 25 years.

What can go into a septic tank?  Domestic waste may go into a septic tank  Industrial waste, solvents, pesticides or fertilizers should not go into a septic tank.  The introduction of toxic materials into a septic tank will kill the biomat layer in the tank. The biomat layer then breaks up and goes into the leachline trenches, clogging the system up. This leads to premature failure.

Farm Labor Housing  Currently, there is no fee for the Department of Environmental Health to review Farm Labor Housing proposals.  The lot must be able to support the additional leachfield that will be required to accommodate the laborers in order for the Farm Labor Housing to be approved.

Future of Septic Systems in San Diego County State Assembly Bill 811 Promulgated by the State Water Board. All Counties are to have standardized requirements for septic systems. “aerobic” septic tanks are to be the norm by Effluent quality will be increased significantly, however the cost of septic systems will triple ( from approximately $7,000 to $25,000). Separation requirement to groundwater will be reduced to 4’. “Alternative” systems will be allowed. All septic systems are to be certified annually that they’re operating correctly by 2007(state Water Board requirement).

Alternative Systems  An “alternative” septic system consists of an aerobic septic tank and a dispersal mechanism. (conventional systems use anaerobic septic tanks).  Oxygen is added to the aerobic tank by various methods. The down-side to aerobic systems is that they have moving parts and require electricity. This opens the door to break-downs and/ or human error.  The positive aspect is that effluent quality is exponentially better.

Alternative Systems (continued)  Since effluent quality is better, it may be possible to reduce the size of the dispersal field. Sizing of alternative systems is in its inceptive stage, and is still being worked out..  4’ separation to groundwater will be required.

Example of a Septic Tank

Tank tied to leachfield

Example of a leachline