Statewide Compliance and Testing

• Overall Compliance: The majority of Montana’s public water systems meet federal Safe Drinking Water Act standards, with comprehensive monitoring programmes managed by Montana DEQ ensuring consistent water quality across the state’s diverse communities. Use our national water quality database to compare Montana data with other states.
• PFAS Monitoring Complete: Montana’s PFAS monitoring under EPA’s Fifth Unregulated Contaminant Monitoring Rule (UCMR5) concluded in December 2025. Kalispell remains the principal affected public water system. Hamilton also detected PFAS but well below health advisory levels. Results are publicly available through Montana DEQ’s website.
• Infrastructure Investment: Montana has received approximately $175 million in federal Bipartisan Infrastructure Law funding since 2022, including $18.9 million specifically for PFAS treatment in small and disadvantaged communities. Kalispell’s nearly $18 million well replacement project — approved by DEQ in January 2026 — is funded through this programme.

Major Water Sources and Challenges

• Yellowstone River System: Primary source for Billings and surrounding communities, with ongoing monitoring for emerging contaminants and seasonal water supply variations from snowpack conditions. See our Billings water quality report for detailed city-level analysis.
• Missouri River Basin: Serves northern Montana communities with support from federal rural water projects, including the Rocky Boy’s/North Central Montana Regional Water System which has received substantial federal investment.
• Rural Water Infrastructure: Montana has received $101.5 million for rural water systems including the Rocky Boy’s/North Central system, Musselshell-Judith Rural Water System, and Fort Peck Reservation/Dry Prairie Rural Water System — critical infrastructure for communities across the state’s vast geography.

PFAS and Emerging Contaminant Update for 2026

• Kalispell Treatment Operating: Ion exchange treatment at the Grandview Wells came into service on 25 September 2025. Post-treatment sampling confirms no detectable PFAS in finished water supplied to consumers, though PFAS remains present in the untreated well source water. Spent media ports are monitored to plan timely filter replacement. Track active advisories on our boil water notice tracker.
• Kalispell Long-Term Solution Approved: In January 2026, Montana DEQ approved an environmental assessment for a nearly $18 million project to drill six new replacement wells, permanently eliminating the PFAS-contaminated Grandview Wells from the system. Public comment closed in February 2026. Funding comes from the federal Emerging Contaminants in Small and Disadvantaged Communities grant programme and Drinking Water SRF loan forgiveness.
• Malmstrom Remediation Extended: The PFAS remedial investigation at Malmstrom Air Force Base — where contamination has been measured at 184 times screening limits — has been extended five years. The full investigation report is expected to be submitted to DEQ in Spring 2026, after which a feasibility study will determine the best remediation approach. Best management practices are in place in the interim, and the base is switching from AFFF foam to fluorine-free alternatives.
• Revised EPA Standards: EPA announced in May 2025 that MCLs for four of the original six regulated PFAS (PFHxS, PFNA, GenX chemicals, and PFBS) would be rescinded. PFOA and PFOS MCLs of 4 ppt each remain, with the compliance deadline extended from 2029 to 2031. Montana DEQ continues its own monitoring programme regardless. If you are concerned, see our recommended PFAS water filters.

Rural and Disadvantaged Communities

• Infrastructure Disparities: Rural water systems face unique challenges with aging infrastructure, limited technical capacity, and higher per-capita costs across Montana’s vast geography. Critically, 94% of rural domestic water comes from unregulated private wells, which can contain arsenic, nitrates, bacteria, and other contaminants not subject to federal monitoring requirements.
• Targeted Federal Support: Dedicated funding through the Emerging Contaminants Small or Disadvantaged Communities programme provides grants to ensure equitable access to safe drinking water in rural Montana. This is the same funding stream supporting Kalispell’s well replacement project.
• Tribal Water Rights: Montana has received $1.37 billion through the Bipartisan Infrastructure Law for Indian Water Rights Settlements, ensuring long-overdue water resources for Montana tribes including the Blackfeet, CSKT, and Crow Nations.

Looking Forward: 2026–2031

Montana’s water quality outlook for 2026 and beyond is cautiously positive. Kalispell’s ion exchange treatment is working as designed, and the approved long-term well replacement project will provide a permanent PFAS solution for Montana’s first affected public water system. The Malmstrom investigation extension is a setback for remediation timelines, but best practices are in place and a feasibility study is forthcoming. The extended federal PFAS compliance deadline to 2031 gives Montana’s smaller water systems more time to plan and fund treatment — though the rescission of four PFAS MCLs reduces the regulatory push to act on those compounds. Rural well owners remain the most vulnerable group, largely outside the regulatory net. Montanans in affected areas — particularly near Kalispell, Great Falls, and communities relying on private wells — are encouraged to review our water quality data, check our live boil water tracker, and consider certified filtration.