Montana Department of Environmental Quality About Us Permitting & Operator Assistance Public Participation

Engineering Infrastructure & Subdivisions

Program Overview

The process of dividing land into parcels is a necessary and important function in the growth of a community. When, where, and how development occurs establishes land division patterns for the community that will last for generations.


Subdivision Review

The DEQ Subdivision Program reviews divisions of land comprising less than 20 acres, as well as condominiums and recreational camping vehicle and mobile home parks, regardless of the size of the parcel where they are located. This review is limited to sanitation facilities, including the water supply, sewage disposal, solid waste disposal, and storm drainage systems.

Subdivisions are reviewed prior to creating the parcels to assure that adequate sanitation facilities can be constructed, operated, and maintained to support each parcel. Planning ahead for proper design and location of the facilities helps protect both our surface and ground water in Montana.

Design manuals have been developed to provide standards for wastewater treatment systems, water supply development, and storm drainage systems. The regulations also set out minimum separation distances between water supply sources and potential contamination sources such as wastewater treatment systems, surface waters, and floodplains.

The regulations and subdivision review are structured to prevent pollution problems through the proper design, location, operation, and maintenance of sanitation facilities.

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Subdivision application training conducted November 2023.
Topic Recording Materials
General Application General Application Recording General Application PowerPoint (PDF)
Onsite Wastewater Onsite Wastewater Recording Onsite Wastewater PowerPoint (PDF)
Nondegradation 101 Nondegradation 101 Recording Nondegradation 101 PowerPoint (PDF)
Onsite Water Onsite Water Recording Onsite Water PowerPoint (PDF)
Stormwater Stormwater Recording Stormwater PowerPoint (PDF)
Other Documents: Nondegradation Predetermination, Sage Grouse Documentation, Waivers/Deviations, Modified Site Plans Other Documents Recording Other Documents PowerPoint (PDF)
DNRC Predetermination DNRC Predetermination Recording DNRC PowerPoint (PDF)
Proposed Rule Changes (2023) Proposed Rule Changes Recording Proposed Rule Changes PowerPoint (PDF)
Municipal Facilities Exclusions (MFEs) Municipal Facilities Exclusions (MFEs) Recording Municipal Facilities Exclusions (MFEs) PowerPoint (PDF)
Nondegradation Continued Nondegradation Continued Recording

Nondegradation Continued PowerPoint Pt 1 (PDF)

Nondegradation Continued PowerPoint Pt 2 (PDF)

Water and Sewer Main Extensions Water and Sewer Main Extensions Recording Water and Sewer Main Extensions PowerPoint (PDF)
Discharge Permits Discharge Permits Recording Discharge Permits PowerPoint (PDF)
Multiple-User Water Systems / Public Water System Two Step Process Multiple-User Water Systems / Public Water System Two Step Process Recording

Multiple-User Water Systems PowerPoint (PDF)

Public Water System Two Step Process PowerPoint (PDF)

What is a Certificate of Subdivision Approval or COSA?
  • A Certificate of Subdivision Approval otherwise known as a COSA is sanitation approval from the Montana Department of Environmental Quality. The COSA outlines what the use of the property is, such as residential or commercial. It also describes what the potable water source will be (well, municipal water system, cistern, etc) and where wastewater will be disposed (drainfield/septic system, municipal wastewater facility). Finally, the COSA describes how stormwater must be mitigated for the site.
My property is not part of a subdivision, do I have a COSA?
  • By definition (MCA 76-4-102(23) a subdivision "means a division of land or land so divided that creates one or more parcels containing less than 20 acres, exclusive of public roadways, in order that the title to or possession of the parcels may be sold, rented, leased, or otherwise conveyed and includes any resubdivision, any condominium, townhome, or townhouse, or any parcel, regardless of size, that provides two or more permanent spaces for recreational camping vehicles or mobile homes.

    In most situations, if your lot was created after 1961 and it is less than 20 acres in size, your property will either have a COSA or it will have sanitary restrictions placed on it. See the FAQ on Sanitary Restrictions. Your local health department is well suited to help you determine if your property has a COSA or sanitary restrictions.
Can I just drill my well anywhere I want to?
  • Well locations are typically shown on the DEQ Approved Lot Layout and have a 100 foot radius well-isolation zone around them.

    In some cases, an "Approved Well Drilling Area" may be illustrated on the lot layout. This drilling area allows the parcel owner to drill the well anywhere within the "Approved Well Drilling Area". The area will be labeled specifically on the Lot Layout and will have a 100 foot well-isolation zone offset from it.

    The well must be drilled in the exact location shown on the Lot Layout or within the "Approved Well Drilling Area" unless a rewrite or modified lot layout is completed. See the FAQ on Rewrites and FAQ on Modified Lot Layouts
What is a mixing zone and can I build in it?
  • The mixing zone is the area in which dilution of the wastewater is assumed to take place. It is defined in 75-5-103 and further defined in 17.30.502(6). As long as setbacks to the drainfield are met, buildings, roads, landscaping, etc. can be constructed in a mixing zone. Drinking water wells may not be installed within 100 feet of a mixing zone, unless previously approved on the DEQ Approved Lot Layout.
How can I get a copy of my COSA and Lot layout?
  • DEQ tries to have digital copies of the COSA and Lot Layouts available, however, local county environmental health departments are the best resource for obtaining copies of these documents.
Can I install an elevated sandmound if I know there is groundwater less than 4 feet from the natural ground surface on my lot?
  • 17.36.320(4) specifically states that there must be four feet of natural soil between the infiltrative surface and a limiting layer such as groundwater. Therefore, an elevated sand mound can not be used on a lot being reviewed under 76-4 MCA to create the 4 feet of separation.

    17.36.320(4) For subsurface systems, a minimum separation of at least four feet of natural soil must exist between the infiltrative surface or the liner of a lined system and a limiting layer. Exceptions to this rule are:
    1. at least six feet of natural soil must exist between the infiltrative surface or the liner of a lined system and a limiting layer on a slope of greater than 15 percent; and
    2. for elevated sand mounds constructed in accordance with Department Circular DEQ 4, the depth of the key may be included as part of the separation distance between the infiltrative surface and a limiting layer.
Do I have to build the house in the location shown on the lot layout?
  • In many cases, the house site illustrated on the lot layout is not the only location that the house can be built. Property owners should work with their local environmental health department and planning department to determine home sites that meet all applicable setbacks.
Do I need a permit to install a drainfield now that I have a COSA?
  • Yes, even thought you have a COSA, a drainfield permit is still required by the local health department.
Can I move my drainfield to a different location on my lot?
  • Many local health departments have the ability to make minor changes to the drainfield and it's location. A Modified Lot Layout or rewrite is required if the drainfield location is greater than 25.0 feet from the soil profile used for siting the approved drainfield location. See the FAQ on Modified Lot Layouts and/or Rewrites.
My COSA states that the lot is for a single family dwelling only, how can I add a second living unit?
  • A rewrite of the COSA will be required to add a second living unit because it changes language in the COSA. See the FAQ on Rewrites.
What is a modified lot layout/revised lot layout?
  • A modified lot layout/revised lot layout is used when changes are needed on the lot layout and the changes do not affect the language in the COSA. Common examples of modified lot layouts are moving a well location or changing the drainfield position.
What are Sanitary Restrictions?
  • Sanitary Restrictions were allowed to be placed on subdivision lots prior to July 1, 1973. These restrictions were placed on the property in order to exempt the property from sanitation review. In some cases, sanitary restrictions were placed automatically on a lot(s) because the lot was required to go through sanitation review at the time the survey was filed but did not receive a COSA prior to filing.

    Finally, after July 1, 1973 many lots were excluded from sanitation review through the use of "no facilities" exemptions. These exemptions are listed on the front of the survey and state something like "Parcel A is excluded from sanitation review by the Department of Environmental Quality pursuant to 17.36.605(2)(a) as a parcel that has no facilities for water supply, wastewater disposal, storm drainage, or solid waste disposal, if no facilities will be constructed on the parcel;"

    In either case, a COSA must be issued for the lot(s) prior to developing facilities that require sewer or water.
What is a COSA Rewrite?
  • A COSA Rewrite is used to change specific requirements outlined in the COSA. For example, a rewrite is required to change the use of a parcel from one living unit to two living units, or from one living unit to one commercial unit. Changing the location of a well or drainfield may not require a rewrite but rather a Modified Lot Layout may be requested. See the FAQ on Modified Lot Layouts.

System Design and Construction

DEQ assists communities with constructing and maintaining wastewater and drinking water infrastructure that provides safe drinking water and produces effluent that protects human health and the environment. DEQ’s engineering staff review plans and specifications for new public water and wastewater systems or requests to modify existing systems to ensure compliance with Design Standards. DEQ is also the administrating agency for the State Revolving Fund Loan Programs that provide below market interest loans for eligible wastewater, drinking water, and nonpoint source pollution projects.

View a chart of current files pending review

Contacts

Subdivisions and Engineering Program Contacts

Bureau Chief
Rachel Clark (406) 444-1277

Program Support Specialist
Candice Gernand (406) 444-4643

Program Support Specialist
Hannah Monday (406) 444-1801


Drinking Water State Revolving Fund

Section Supervisor
Jake Goettle (406) 444-6824

Water Pollution Control State Revolving Fund

Section Supervisor
Mike Abrahamson (406) 444-6776

Public Water Supply

Section Supervisor
Jackie Kuhl (406) 444-1515

Subdivision Review

Section Supervisor
Shawn Rowland (406) 444-6727

Subdivision Rule Revisions 2023: Phase 2

The second phase of the subdivision rule update was adopted December 22, 2023.  Information about the rule adoption can be found at the following link. Phase 2 Rule Update Public Notice

Associated Materials:

MAR Notice No. 17-430 Notice of Adoption and Amendment (Montana Administrative Register 2023, Issue No. 24, December 23, 2023, Pages 1861-1862) 

MAR Notice No. 17-430  Notice of Public Hearing on Proposed Adoption and Amendment (Montana Administrative Register 2023, Issue No. 16, August 25, 2023, Pages 786-805)

DEQ/Local Government Joint Application Form

Checklists, Fees, & Flowcharts

DEQ Circulars and Regulations

Nondegradation Determination

Municipal Facilities Exclusion

Subdivision Stormwater Design Criteria and Resources

The public water and wastewater engineering review program reviews plans and specifications for new systems and alterations to existing systems. Approval from DEQ is required to construct, alter or extend a public sewer system serving 15 or more families or 25 or more persons daily for any 60 or more days in a calendar year.

  1. Prior to operating, constructing, altering or extending a public water supply, the applicant must submit an engineering report along with the necessary plans and specifications to DEQ or a delegated division of local government for review and written approval.
  2. The engineering report, plans, and specifications for a community public water supply must be prepared and designed by a professional engineer according to specific engineering criteria. An engineer may be required to prepare plans and specifications for a noncommunity public water supply when the complexity of the proposed system warrants that level of involvement by an engineer.
  3. The applicant must identify the legal entity responsible for the ownership, operation, maintenance, and perpetuation of the public water supply system. If a change of ownership occurs, DEQ must receive written notice within 30 days.
  4. The department has 60 days to approve, approve with conditions, deny the application, or to request more information. The DEQ or a delegated division of local government will issue a written approval for a public water supply system if it determines that the design report, plans, and specifications are complete and the applicant has complied with department rules.
  5. If construction, alteration, or extension of the community public water supply system has not been completed within three years after approval, the applicant must resubmit all of the information required in items one through three above.
  6. Within 90 days after the construction, alteration, or extension of the public water supply system, the project engineer must certify to DEQ that the required work was completed according to the approved plans and specifications.

Plan Review Fee Record Design Criteria

Environmental Assessments, Categorical Exclusions and Findings of No Significant Impact

Forms and Checklists

Water/Sewer Main and Water Supply Well Checklists

The Montana Legislature established two State Revolving Fund (SRF) Loan Programs - one for water pollution control projects (wastewater and non-point source projects) and the other for drinking water projects. Both programs provide at or below market interest rate loans to eligible Montana entities.

Drinking Water Project Funding

The Drinking Water State Revolving Fund (DWSRF) program is a federal-state partnership to help ensure safe drinking water. The program provides financial support to water systems and to state safe water programs.

Types of Financial Assistance:

Types of assistance currently provided are direct loans and purchase or refinancing of existing

Financial Requirements:

  • Financial capability to properly operate the system and to repay the loan
  • Loan secured by a Bond or Note
  • Different bonding & security options exist (Revenue, general obligation, SID, RSID, tax increment)
  • Revenue Bond requires debt service reserve and coverage of 110%.
  • Maintain financial records

Terms:

The current interest rate is 2.5 percent with payment schedules not to exceed 20 years. Drinking Water Projects qualifying as disadvantaged may extend term up to 30 years.

Funds Available:

The SRF loan programs are designed to provide a perpetual source of financial assistance to Montana communities.


Waste Water Project Funding

The Water Pollution Control State Revolving Fund (WPCSRF) Program was established for water pollution control projects. The program provides at or below market interest rate loans to eligible Montana entities.

Examples of Eligible Water Quality Projects

Wastewater Projects:

  • Wastewater treatment plant improvements
  • Interceptors, collectors, and lift stations
  • Lagoon construction & rehabilitation
  • Engineering & project inspection
  • Land used for disposal purposes

Non-Point Source Projects:

  • Agricultural BMPs
  • Urban storm water /construction runoff
  • Animal feed operations (AFOs)
  • Wetlands/Stream bank restoration
  • Underground storage tanks
  • Septic system removal or upgrade

Types of Financial Assistance

Types of assistance currently provided are: direct loans and purchase or refinancing of existing debt.

Financial Requirements

  • Financial capability to properly operate the system and to repay the loan
  • Loan secured by a Bond or Note
  • Different bonding & security options exist (Revenue, general obligation, SID, RSID, tax increment)
  • Revenue Bond requires debt service reserve and coverage of 110 percent
  • Maintain financial records

Terms:

The current interest rate is 2.5 percent with payment schedules not to exceed 30 years for certain projects.

Funds Available:

The SRF loan programs are designed to provide a perpetual source of financial assistance to Montana communities.


How to Apply

To begin the application process, all entities must request that their project(s) be added to the Priority List contained in the Intended Use Plan. Early notification by the applicant is essential to get on the priority list and a project remains on the list until it has been completed regardless of the funding source(s) used to finance the project. This annual process begins in the Spring to identify projects which may need SRF funding for their project in the upcoming year.

The WPCSRF Survey Form or the DWSRF Survey Form is required to be placed on the Project Priority List. Please COMPLETE and submit to DEQ Engineering Bureau with supporting information.

Once ready to begin the project, applicants must submit the Uniform Application Form For Montana Public Facility Projects to request SRF loan funding. These applications are accepted year round. After the application is evaluated and approved, funds can be committed to a project. The SRF loan program cooperates with the other funding programs to ensure project funding is available when it is needed.

Loans will be offered on a first-come basis until the demand exceed the available funds. Lower ranked projects may be funded before higher ranked projects (if the higher ranked project is not ready to proceed) as long as the funds are available. Ranking on the priority list is based on water quality and/or public health impacts and financial needs.

Additional Financial Assistance Programs for Water, Wastewater, and Solid Waste Projects

Intended Use Plans and Project Priority List

2024 Intended Use Plans and Project Priority Lists

Drinking Water | 2024 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2024 Intended Use Plan and Projecty Priority List (Final)

2023 Intended Use Plans and Project Priority Lists

Drinking Water | 2023 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2023 Intended Use Plan and Projecty Priority List (Final)

2022 Intended Use Plans and Project Priority Lists

Drinking Water | 2022 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2022 Intended Use Plan and Project Priority List (Final)

2021 Intended Use Plans and Project Priority Lists

Drinking Water | 2021 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2021 Intended Use Plan and Project Priority List (Final)

2020 Intended Use Plans and Project Priority Lists

Drinking Water | 2020 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2020 Intended Use Plan and Project Priority List (Final)

2019 Intended Use Plans and Project Priority Lists

Drinking Water | 2019 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2019 Intended Use Plan and Project Priority List (Final)

2018 Intended Use Plans and Project Priority Lists

Drinking Water | 2018 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2018 Intended Use Plan and Project Priority List (Final)

2017 Intended Use Plans and Project Priority Lists

Drinking Water | 2017 Intended Use Plan and Project Priority List (Final)
Water Pollution Control | 2017 Intended Use Plan and Project Priority List (Final)

Lead Service Line Intended Use Plans and Project Priority List

Emerging Contaminant Intended Use Plans and Project Priority List

Reports