After years of work, the Flathead Basin Commission released a map this spring identifying the highest potential risks from septic systems in the Flathead Basin. Many populated areas near bodies of water like Flathead Lake and Lake Mary Ronan were identified as “very high-risk,” meaning there is potential for septic systems to leak into the groundwater and, eventually, the surface water.

The commission had hoped the map would be a tool for planners and policymakers. Nutrient pollution is a leading cause of water impairment in the state, according to the Montana Environmental Information Center, and nutrients often get into the water via “nonpoint sources,” such as leaking septic systems or agricultural runoff, that accumulate into larger problems.