A New Solution for Onsite Septic Systems:

We are proud to introduce the Advanced Enviro-Septic® Treatment System (“AES”) in Montana. Advanced Enviro-Septic® is the next generation of our effective and reliable Enviro-Septic® technology; certain systems have received Class I Certification under NSF International/ANSI’s Standard 40 for Wastewater Treatment Devices. Pending revision of its Circular 4 Design Standard, Montana DEQ has given AES product interim approval by formally issuing the following blanket deviations:


The following deviations to Montana Circular 4 Design Standards can be used for non-public wastewater systems (those that serve less than 25 people for 60 days) with residential strength waste and a design capacity of less than 2,500 gpd.

  • DEQ-4, Standard Presby laterals may be placed a minimum of two feet on center with zero distance between trench walls. The centerline-centerline distance between the two outermost pipe laterals shall not exceed 14 ft.
  • DEQ-4, Standard For the purposes of sizing, Presby lateral trenches must not be considered more than 48 inches wide.
  • DEQ-4, Standard 13.2.3: Presby lateral trenches may use gravity distribution up to 48 inches.
  • DEQ-4, Standard 13.2.4: When installing a Presby system, the absorption system size in square footage per Chapter 8 may be reduced in size by 50 percent for soil percolation rates less than 51 mpi and 25 percent for soil percolation rates between 51 and 120 mpi..

For application of AES to public wastewater systems (those that serve more than 25 people for 60 days and a design capacity of less than 2,500 gpd) or to systems with greater than residential strength waste, Montana DEQ will consider granting a variance.

Certification class:

We require individuals who wish to design or install an  Advanced Enviro-Septic® or Enviro-Septic® System be certified by attending the Enviro-Septic® Design and Installation Certification Class. The class offers various design and installation configurations, troubleshooting techniques and tricks of the trade. To view the class schedule and certification options click on the ‘Training and Certification’ tab above.


Montana Design & Installation Manual 2016