Conventional vs. Alternative Septic Systems in San Diego County: When Is Advanced Treatment Needed?

If you're building or developing a property in San Diego County, you may hear several different terms during the septic process: conventional septic, OWTS, alternative system, advanced treatment, STS or supplemental treatment system.

They all relate to onsite wastewater treatment, but they don't necessarily mean the same thing.

For many properties, a conventional septic system is sufficient. Other sites require additional wastewater treatment because of the property's conditions or the requirements of the approved design.

Understanding the difference can help you know what to expect if your OWTS professional tells you that your property needs something beyond a conventional septic system.

What Is a Conventional Septic System?

A conventional septic system is an Onsite Wastewater Treatment System (OWTS) that generally uses a septic tank followed by an approved subsurface dispersal system.

Wastewater from the home enters the septic tank, where solids settle and wastewater receives primary treatment. The liquid effluent then moves to the dispersal system, where it is distributed into the surrounding soil for additional treatment and disposal.

Depending on the approved design and site conditions, San Diego County conventional dispersal methods can include options such as:

• Leach lines

• Approved chamber systems

• Deep beds

• Vertical seepage pits in qualifying locations

The system approved for a particular property depends on site-specific conditions and County requirements.

What Is a Supplemental Treatment System?

San Diego County uses the term Supplemental Treatment System (STS) for an OWTS that provides advanced or supplemental treatment beyond the primary treatment occurring in a standard septic tank.

Depending on the system and project, supplemental treatment may be designed to provide additional treatment for nitrogen, pathogens or both before wastewater reaches the final dispersal system.

You may also hear people refer to these systems more generally as:

• Advanced treatment systems

• Alternative septic systems

• Advanced OWTS

• ATUs, or aerobic treatment units

• Supplemental treatment systems

The terminology can be confusing, but the important distinction is that these systems add another treatment process beyond what occurs in a conventional septic tank.

Why Would a Property Need Advanced or Supplemental Treatment?

Usually, it isn't because someone simply decided they wanted a more complicated septic system.

Supplemental treatment may be considered or required because of the property's site conditions, environmental constraints or approved OWTS design.

One important example is groundwater separation.

San Diego County generally requires conventional septic designs to maintain at least five feet of separation between anticipated high groundwater and the bottom of the dispersal system. The County explains that supplemental treatment can, in qualifying circumstances, allow that separation to be reduced to two feet.

Other factors that can affect OWTS feasibility and design include:

• Soil characteristics

• Percolation rates

• Groundwater

• Slope

• Available dispersal area

• Property setbacks

• Proposed wastewater flow

• Water-quality considerations

• The type and size of development proposed

This is why two neighboring properties can sometimes end up with very different septic solutions.

Does a Difficult Property Automatically Need an Alternative System?

No.

A challenging site doesn't automatically mean that supplemental treatment will solve the problem—or that it is the appropriate solution.

San Diego County requires site evaluation and testing as part of determining what type of OWTS can be approved for a property.

For supplemental treatment systems specifically, the County requires percolation testing and a design prepared by a licensed OWTS Professional.

The Qualified Professional evaluates the site and determines the appropriate system design. The septic installer then constructs the system according to the approved plans.

Are Supplemental Treatment Systems More Expensive?

Generally, yes.

San Diego County's current Local Agency Management Program specifically acknowledges that the design, installation, operation and maintenance associated with supplemental treatment systems can be more complex and expensive than a standard OWTS.

The initial installation isn't the only consideration.

Supplemental systems in San Diego County are also subject to ongoing operating and maintenance requirements. Current County requirements include an annual operating permit, an approved Operations and Maintenance Plan, an ongoing maintenance contract with a Qualified Service Provider and periodic inspections.

For that reason, property owners should understand both the initial construction cost and ongoing ownership requirements before proceeding with a supplemental system.

What Types of Advanced Septic Systems Are Available?

There isn't one universal “alternative septic system.”

Different technologies provide different types of treatment and may be incorporated into an OWTS depending on the approved design.

Red Rock Industrial has installation experience with a variety of advanced and alternative wastewater technologies, including systems and components from manufacturers such as:

• Advanced Enviro-Septic / Presby

• Jet

• Norweco Singulair

• Anua

• Aerofin

• Puraflo

• GeoFlow

• SludgeHammer®

The system appropriate for a particular property should be determined by the project's OWTS Qualified Professional and approved for the specific application.

Can an Alternative System Make an Otherwise Unbuildable Property Work?

Sometimes—but this is an area where property owners should be careful about assumptions.

Supplemental treatment can address certain wastewater-treatment or site constraints, but it does not eliminate every physical requirement associated with an OWTS.

A property still needs an approved means of dispersing treated wastewater, appropriate setbacks and sufficient site conditions for the proposed system.

Before purchasing land or designing a project around the assumption that an advanced septic system will make development possible, have the property evaluated by a qualified OWTS professional.

Who Installs Advanced Septic Systems in San Diego County?

Supplemental treatment systems require specialized installation experience.

Under San Diego County's current LAMP, licensed installers performing supplemental-treatment installations must be experienced and competent with this type of work, follow the engineer's design and manufacturer's specifications, and be trained or certified by the manufacturer for the specific treatment system being installed.

Red Rock Industrial is a San Diego County-approved septic installer with experience installing both conventional OWTS and specialized treatment systems.

Red Rock Industrial is also currently the only authorized SludgeHammer® installer in San Diego County.

Conventional or Advanced—Start With the Property

The best septic system isn't necessarily the simplest system or the most advanced technology.

It's the system that is appropriate for the property's conditions, proposed development and approved OWTS design.

If you're planning a new home, ADU, replacement septic system or other development on a San Diego County property, begin by having the site and wastewater requirements properly evaluated.

Once you have an approved design, Red Rock Industrial can help take the project from plans to underground installation.

Already have septic plans or an OWTS design?

Contact Red Rock Industrial to discuss the installation scope and request an estimate.

→ Learn more about our Septic System & OWTS Installation services in San Diego County.