Skip Navigation Links Home / Water Quality Information / Public Water Supply / Regulated Activities / Wastewater (Sewer) Systems

Wastewater (Sewer) Systems

Regulated Activities

Approval from the Montana Department of Environmental Quality (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. Operators in charge of public wastewater treatment systems must be licensed by the DEQ.

Application Requirements

  1. Prior to operating, constructing, altering or extending a public sewer system, the applicant must submit an engineering report along with the necessary plans and specifications to the DEQ or a delegated division of local government for review and written approval.
  2. The engineering report, plans and specifications for a public sewer system must be prepared and designed by a professional engineer licensed in the state of Montana according to specific engineering criteria developed by the department.
  3. The applicant must identify the legal entity responsible for the ownership, operation, maintenance and perpetuation of the public sewer system. If a change of ownership occurs, the 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 sewer 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 public sewer system has not been completed within three years after approval, the applicant must resubmit all of the information required in 1-3 above.
  6. The proposed public sewer system must comply with the Montana Water Quality Act.
  7. Within 90 days after the construction, alteration or extension of the public sewer system, the project engineer must certify to the DEQ that the required work was completed according to the approved plans and specifications. The project engineer must also provide as built drawings at this time.


Wastewater treatment operators must pay a $70 application fee that entitles the applicant to take one or more exams for 12 months from the date of application. Each exam is $70. The annual renewal fee is $40 and must be postmarked or delivered to the department by June 30th.