Septic System Permitting Process

Applicant:  A permit is required to install and operate a sewage treatment system (septic system) in Flathead County.  Apply at Environmental Health.  It is extremely important to provide the property’s legal description.  Newly created property can get a physical address  from GIS Address Improvement at https://flathead.mt.gov/gis/addressing.php.

Click here to view the septic system application process.

Site Review vs. Site Evaluation:

 Before a permit is issued, your property will be evaluated to determine if installing a septic system will comply with County and State regulations.

  1. PREAPPROVED: An EVALUATION may have been done when your property was created*   or prior to you owning the property. If this is the case and you are not relocating the septic system, a “SITE REVIEW” is required with a fee of $100.

  2. SITE REVIEW process: The applicant or their representative must physically stake and label 1) the 4 corners (~ 40’ x 100’) of the approved drainfield site, 2)  the well location, and 3) the proposed house site.  Contact Environmental Health when the staking is complete.

  3. NEVER APPROVED OR OLD APPROVAL: All other property must have a SITE EVALUATION which usually requires a soils determination (test hole), possible groundwater monitoring, and non-degradation analysis conducted to comply with the Montana Clean Water Act to protect surface and ground water.  The Site Evaluation fee is $225 and the Non-degradation fee is $200.

Department:  The applicant will receive a “Site Evaluation and Design Report” from Environmental Health after the Site Review or Site Evaluation has been completed which they  must provide to a designer (or engineer) certified by this office.

Applicant:  A completed Hydraulic Design (Pump or Siphon) and Detailed Drainfield Layout (i.e., site plan) must be prepared by the certified designer or professional engineer and returned to Environmental Health.

Department:  Upon approval of the design, a permit will be issued.

The permit fee will be dependent upon Class of System permitted.

  • Class 1 System– an individual or single family sewage treatment system–$300.00

  • Class 2 System- a shared, multi user or public sewage treatment system with design flow of less than 1000 gallons per day–$415.00

  • Class 3 System– a shared, multi-user or public sewage treatment systems with design flow of 1000 or more gallons per day–$475.00 +$0.15/gal over the first 1000 gallons.

*WHAT IS A COSA? 

In Montana when property is subdivided into lots less than 20 acres, an environmental review is required through the Montana Department of Environmental Quality (DEQ).  A consultant does the environmental work such as determining soil type, if groundwater quality will be excessively degraded (Non-degradation analysis), topography, limiting factors, storm water drainage, etc.   Once the State reviews and approves the environmental work a Certificate of Subdivision Approval (COSA) is issued describing specific requirements for the property and showing a site design where the sewage treatment system and well must be located.  This is different from Planning and Zoning or Homeowner’s Association rules.

  • New landowners should receive this documentation when they purchase the property.  If you have not received this documentation, contact your realtor or this office.

  • If the landowner wishes to alter the requirements stated in the COSA, they must contact a consultant to re-write the approval.