Seeley Lake Special Management Area

Let us know your questions on the Seeley Lake groundwater nitrate levels and Special Management Area.

Seeley Lake’s groundwater is contaminated with elevated levels of nitrates because of a combination of dense development served completely by on-site septic systems and the unique geology of the aquifer below the community.

Missoula Public Health is required by state law to protect the environment and human health. When staff became aware of the nitrate contamination issue in Seeley Lake in 2011, they re-evaluated the way individual septic permits are reviewed and approved, as required by state laws and the City-County Health Code, and established a boundary where this contamination needs to be mitigated. This ensures any new development within that boundary does not make the existing contamination worse. The Health Board then acknowledged this boundary as a Special Management Area in 2015 in Regulation 1 of the Health Codes, and there have been no changes to this regulation language since 2015. Learn more about what an SMA is below, and note Seeley Lake is not the only SMA in Missoula County.

The Seeley Lake Sewer District had been collecting fees since its inception in 1992, and also received numerous grants. In 2021, a question was placed on the ballot for voters in the sewer district to decide whether to pass two bond measures that, along with the grants and fees collected, would have paid to construct a sewer. The voters rejected the two measures, and the sewer district had to return all the funding received for the project.

In 2024, MPH offered to conduct a groundwater flow direction study, using new monitoring wells. In addition, MPH will take over the responsibility for testing for about one year. This will not only save the sewer district money, but it will also provide valuable data to inform future decisions. This study is ongoing and will conclude sometime in 2025.

The current Sewer District Board has recently gained momentum toward a community-wide solution. Their consulting firm is evaluating several sewer system options for the community and compiling a list of pros and cons in terms of cost, level of treatment and location. The Sewer District, MPH, and the State and County Offices of Emergency Management are working to secure funding for the planning and construction of the chosen sewer system.

This project is longstanding and affects nearly everyone in the community. To understand the full scope of how we got to where we are today, read the full story below and the FAQs on the right-hand side, and let us know any questions you have.

In the end, we all have a clear, common goal: ensuring Seeley Lake residents live in a safe and healthy environment and protecting the natural resources in this area.