PFAS · Montana

PFAS in Montana drinking water: EPA’s final survey results

EPA’s national PFAS survey (UCMR 5) tested 40 of the community water systems that serve homes in Montana. 5 found at least one of 29 PFAS above the laboratory reporting level, and 0 had a PFOA or PFOS sampling-location yearly average at or above EPA’s 4.0 ppt limit. Samples were collected from January 2023 to February 2026.

In focus13%of surveyed systems found PFAS

Public records. Clearer context.

Data as of EPA UCMR 5 final release, August 2026 (file dated Aug 28, 2026) · EPA SDWIS 2026Q2 (file dated Jul 9, 2026). How we build these pages

Montana community systems in EPA’s survey

serving about 565,045 people

found at least one PFAS

13% of surveyed systems; about 43,767 people served

PFOA or PFOS yearly average at or above the MCL

compared the way EPA does: the average of a complete sampling set

lithium at or above EPA’s health reference level

lithium was part of the same survey

PFBS was the compound Montana community systems found most often: 2 of 40 tested systems measured it above the reporting level. Across the country, 35% of surveyed community systems found at least one PFAS; in Montana the share is 13%. The largest Montana system with a detection, Kalispell Public Works, serves 25,000 people and found 2 of the 29 compounds.

Which PFAS were found most often in Montana

Each row counts the Montana community water systems where that compound was measured above the reporting level at least once. A detection is a measurement, not a violation: most of these compounds have no federal limit.

Compound	Systems where found	Systems tested	Share
PFBS	2	40	5%
PFOS	2	40	5%
PFBA	1	40	3%
PFHxS	1	40	3%

Montana systems with the most PFAS found

The 5 surveyed community water systems that found the most different PFAS, with PFOA and PFOS compared to EPA’s 4.0 ppt limits on the yearly average at the highest sampling location. Larger systems come first when counts tie.

Water system	People served	PFAS found (of 29)	PFOA	PFOS
Kalispell Public Works MT0000259	25,000	2	— not detected above the reporting level	3.3 ppt below the MCL
Malmstrom Air Force Base MT0000515	8,850	1	— not detected above the reporting level	— not detected above the reporting level
Hamilton City of MT0000234	5,660	1	— not detected above the reporting level	— not detected above the reporting level
Big Sky County Water and Sewer Dist 363 MT0002385	4,132	1	— not detected above the reporting level	— not detected above the reporting level
Alpine Village Wua MT0003229	125	1	— not detected above the reporting level	2.1 ppt below the MCL

Counties with the most systems that found PFAS

Flathead County 2 of 6 surveyed systems
Cascade County 1 of 3 surveyed systems
Ravalli County 1 of 2 surveyed systems
Madison County 1 of 1 surveyed systems

How to read these numbers

UCMR 5 asked every community and non-transient non-community water system serving 3,300 or more people, and a sample of smaller ones, to test for 29 PFAS and lithium. EPA published the final data in August 2026; its samples were collected from January 2023 to June 2026. A system that was not in the survey has no result here; that is not the same as having no PFAS.

UCMR 5 is a one-time national monitoring survey. Its results do not indicate compliance or non-compliance with the PFAS Maximum Contaminant Levels, which are enforced on running annual averages and take effect in 2029 (EPA has proposed allowing extensions to 2031). A single result above a limit on this page is a measurement, not a violation.

See how to read UCMR 5 results and our methodology for how systems are matched to places.

After Montana’s PFAS results

Find your system. Then read its report.

State recordsAll Montana water recordsCounties, ZIP reports, lead results and violations for the whole state.FiltersChoosing a PFAS filterHow to check a filter’s certified PFAS reduction before you buy.Your utilityFind your annual water reportYour utility’s Consumer Confidence Report will list its own PFAS results and any treatment plans.

County pages

Montana water records

Sources

EPA UCMR 5 occurrence data, samples collected 2023-01-03 – 2026-06-17, final release, August 2026 (file dated Aug 28, 2026); EPA SDWIS via ECHO, 2026Q2 extract (file dated Jul 9, 2026); EPA service-area boundaries v3.0; Census 2020 ZCTAs. Database prepared 2026-09-03.