Missoula County backs intent to adopt updated on-site wastewater rules

Missoula County commissioners on Thursday approved a resolution of intent to adopt an updated Regulation 1 of the Missoula City-County Health Code to allow some new on-site wastewater systems in engineered fill.

The change follows the Montana Department of Environmental Quality(DEQ) rule update, and the Missoula City-County Board of Health approved the revised regulation on April 17, 2025, recommending the governing bodies adopt it by reference.

Charles "Charlie" Shane, environmental health manager at Missoula Public Health, told the commissioners that DEQnow permits some replacement and new on-site systems in engineered fill after the 2023 Legislature directed the agency to revise rules. "Health code rules must be at least as stringent as state rules," Shane said, and the local change would allow property owners "more flexibility when siting systems on difficult or disturbed sites." He added that DEQ requires engineered design reports, additional soil testing and certified as-builts before final approval.

Shane warned that fill systems were previously prohibited because "if they are constructed improperly, wastewater can surface and that would potentially expose people, animals, pests to pathogens that are present in wastewater." He said the new state requirements include design and construction criteria intended to prevent that outcome.

County staff said the local interlocal agreement requires both the county commissioners and Missoula City Council to adopt the health code changes before they take effect. The recommended local action would replace the version adopted by reference under Ordinance 2022-03 with the health board-approved text from April 17, 2025.

Commissioners moved and seconded a motion to pass a resolution of intent to adopt an ordinance revising Regulation 1, and the motion carried with all present voting "aye." The action is a resolution of intent; final ordinance adoption will follow the county's ordinance process and requires a later formal ordinance vote by the governing body.

The updated rule text clarifies that fill may not be used to circumvent state horizontal or vertical setbacks or other siting limits and that fill materials must meet specified soil types and compaction, per DEQ guidance. Missoula Public Health will continue to require sanitation review and certification in each case; staff said certain systems will require engineered designs and as-built certifications before final approval.