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Types of Septic Systems and Allowable Building Improvements

Six primary types of septic systems are recognized, depending on the history of the system, the characteristics of the property, and the desires of the owner to upgrade the structures. If a parcel cannot meet the requirements for a Standard System, a proposal for a Nonstandard System must be submitted. Additional requirements are also specified for large systems and systems in sandy soils.

  1. A Standard System meets all of the standard requirements and enables building additions consistent with the number of bedrooms for which the septic system is sized, and consistent with building and zoning department regulations. No construction may occur over the septic system and/or expansion area.
     
  2. Nonstandard Systems do not meet all the requirements for a standard system, but they do meet the more specialized requirements for the different types of nonstandard systems. Approval of a nonstandard system requires recordation of a notice of nonstandard system on the deed, special operating requirements, and payment of an annual inspection fee to confirm continued satisfactory performance (fee waived for Limited Expansion Systems). Five types of nonstandard systems are recognized:
  • An Alternative System utilizes a specific alternative technology to meet requirements and may enable bedroom and other additions if the proposed system design can accommodate the wastewater peak flow.
     
  • A Limited Expansion System is a permitted system repair that meets all of the requirements for a standard system except for groundwater separation (at distances over 250 feet from a waterbody), or expansion area. Use of a Limited Expansion system requires water conservation measures and enables only a one time addition of up to 500 sq.ft. of conditioned space with no bedroom additions, and no increase in the volume of wastewater discharge. Additions will not be approved which encroach on the septic system or any area of the property needed to install a replacement system which meets the requirements for a standard system to the greatest extent possible. As long as the system performs well, no annual inspection fee will be charged.
     
  • A Low-Flow System is a permitted system repair that meets all of the requirements for a standard system except for leachfield area or size of pump chamber for pump up systems. Use of a Low-Flow system requires water conservation measures and enables only a one time addition of up to 500 sq.ft. of conditioned space with no bedroom additions, and no increase in volume of wastewater discharge. Additions will not be approved which encroach on the septic system or any area of the property needed to install a replacement system which meets the requirements for a standard system to the greatest extent possible. An annual inspection fee will be charged on the tax bill.
     
  • A Haulaway System is a system that requires that effluent be pumped out on a seasonal or full time basis to prevent failure, and/or ensure that requirements for groundwater separation are met. Use of a haulaway system enables only a one time addition of up to 500 sq.ft. of conditioned space with no bedroom additions or increase in volume of wastewater discharge. An annual inspection fee will be charged on the tax bill.
     
  • An Enhanced Treatment System is a system that utilizes special designs and/or additional technology to treat the effluent to a much higher level than a conventional system. The goal is to reduce BOD, Suspended Solids and Nitrogen each to less than 10 mg/l. (In the interim, technologies which meet the objective for BOD and Suspended Solids and provide at least 50% nitrogen removal may be accepted. In sandy soils, special designs which promote denitrification in or under the leachfield will also be considered.) Enhanced Treatment systems will be Alternative Systems and may utilize higher application rates in the leachfield design if they meet the objectives for BOD and Suspended Solids removal (see Section II.D). Enhanced treatment systems are required in the following circumstances:
    • For systems in Sandy Soils in the San Lorenzo Watershed and Water Supply Watersheds. Reference maps are maintained at the EHS office. Sandy soils are those soils identified by the US Soil Conservation Service as Zayante or Baywood Series, or other soils found in the field to have percolation rates faster than 6 MPI). Enhanced treatment shall be required for any new system and any system which will serve a bedroom addition, a remodel adding more than 500 square feet, or other expansion of use which will result in an increase in volume or strength of wastewater flow. Ultimately, enhanced treatment will likely be required for all repairs in sandy soils.
       
    • For Large Systems which serve more than 5 residential units or which have peak daily flows greater than 2500 gallons per day and are located in the San Lorenzo Watershed or a designated Water Supply Watershed. For all new or replacement systems in the designated areas, enhanced treatment shall be required.
       
    • A Prestandard System is an existing septic system installed prior to 1993 which shows no indication of failure, but which does not meet requirements for a standard system. Without any further upgrade (but with a satisfactory septic pumpers inspection report), such a system enables only a one time addition of up to 500 sq.ft. of conditioned space with no bedroom additions or increase in volume of wastewater discharge. Additions will not be approved if they will encroach on the septic system or any area of the property needed to install a replacement system which meets the requirements for a standard system to the greatest extent possible.

Standard System

The requirements for new individual onsite wastewater disposal systems as set forth in Chapter 7.38 of the County Code and in the Water Quality Control Plan for the Central Coast Basin shall be met to the greatest extent possible for all system repairs and upgrades. At a minimum, the following requirements shall be met.

SEPTIC TANK REQUIREMENTS

  1. Tank Size - For residences with 1 to 4 bedrooms, tank size shall be 1500 gallons, with an additional 250 gallons per bedroom for each bedroom in excess of 4.  For commercial or institutional sewage disposal systems, the septic tank volume (independent of any grease traps required) shall be three times (3x) the peak daily flow. When repairing or upgrading commercial or institutional septic systems, the applicant must present at least two years of past water use records and/or a plausible projection of future peak daily wastewater flows.
    Exterior grease traps, sized and installed to conform to EHS policy, shall be required on commercial/institutional facilities discharging grease laden waste. The pumping of grease traps as often as necessary to prevent grease entering the leachfield(s) shall be a condition of any food facility Health Permit.
     
  2. Tank Type - Concrete, fiberglass and polyethylene septic tanks from approved manufacturers are the only septic tanks permitted for tank replacements. Existing, two chambered redwood fiberglass, or concrete septic tanks 800 gallons or larger that are in good condition do not require replacement at the time of septic system repair and will be recognized as passing an inspection for loan review purposes. Other tank types may be allowed provided adequate documentation of satisfactory performance is provided.
     
  3. Access to Tank - Septic tanks should be installed within 12 inches of the ground surface when possible. If it is demonstrated that the building sewer pipe cannot be modified and the top of a septic tank must be deeper than 12 inches from the ground surface, the tank shall be modified so as to extend all manholes and covers to a minimum of 12 inches from the ground surface. Material used to extend the manholes and covers shall be of the same material as the septic tank. Septic tanks placed in paved driveways shall be provided with "traffic grade" concrete access manholes with cast iron lids. A cleanout to finished grade shall be provided between the building and the septic tank. 3" or 4" Schedule 40 ABS pipe shall be used to connect the building drains to the septic tank.
     
  4. Setbacks for Tank Installation - Septic tanks shall be installed to conform to the following minimum setback distances:
    • From Septic Tank to Leaching Device - minumum of 3 Feet
    • From Septic Tank to Property Line, Easement or Right-of-Way - minumum of 5 Feet
    • From Septic Tank to Foundations, Structures, Decks - minumum of 5 Feet
    • From Septic Tank to Water Line - minumum of 10 Feet
    • From Septic Tank to Stream, Well, Spring, or Watercourse - minimum of 50 Feet
       
  5. Water Tight Tanks - For all repairs in areas of suspected high groundwater and/or utilizing pumps, water tight tanks and risers shall be required. Water tightness shall be ensured by filling the tank and riser with water and observing that the level does not drop by more than 1/4 inch in 12 hours. Plastic tanks will not be allowed in suspected high groundwater areas unless provisions approved by the manufacturer are made to prevent the tank from floating or collapsing when pumped during conditions of high groundwater.