Montana Water Report Card: Worst Water Systems
The most contaminated public water systems in Montana, ranked by PFAS levels, lead, and EPA violations from official EPA data.
Quick Answer
Malmstrom Air Force Base has the highest PFAS in Montana at 7 ppt (2x the EPA limit). Big Mountain Water Company has the highest lead at 56 ppb. The tables below rank the worst systems in each category so you can see how your water compares.
Highest PFAS Levels in Montana
Public water systems in Montana with the highest peak PFAS ("forever chemical") reading in EPA UCMR5 testing (2023-2025). The EPA enforceable limit for PFOA and PFOS is 4 ppt.
| # | Water System | Location | Peak PFAS (ppt) | Compounds | vs 4 ppt limit |
|---|---|---|---|---|---|
| 1 | Malmstrom Air Force Base | Malmstrom Air Force Base · 8,850 served | 7 | 1 | 2x |
| 2 | Kalispell Public Works | Kalispell · 25,000 served | 6.6 | 2 | 2x |
| 3 | Alpine Village Wua | Columbia Falls · 125 served | 4.1 | 1 | 1x |
Highest Lead Levels in Montana
Community water systems in Montana with the highest 90th-percentile lead result under the EPA Lead and Copper Rule. The EPA action level is 15 ppb; there is no safe level of lead for children.
| # | Water System | Location | Lead 90th-pctile (ppb) | vs 15 ppb |
|---|---|---|---|---|
| 1 | Big Mountain Water Company | Whitefish · 2,435 served | 56 | 3.7x over |
| 2 | Roundup Water Department | Roundup · 1,900 served | 41 | 2.7x over |
| 3 | Missoula Water | Missoula · 68,200 served | 22 | 1.5x over |
| 4 | Baker City Of | Baker · 1,858 served | 14 | within |
| 5 | Townsend City Of | Townsend · 2,000 served | 13 | within |
| 6 | Great Falls City Of | Great Falls · 60,000 served | 12 | within |
| 7 | St Mary Headquarters And Cg | West Glacier · 1,030 served | 10 | within |
| 8 | Glasgow City Of | Glasgow · 3,253 served | 9 | within |
| 9 | Scobey City Of | Scobey · 1,026 served | 9 | within |
| 10 | Manhattan Town Of | Manhattan · 1,800 served | 8.1 | within |
| 11 | Anaconda Water Department | Anaconda · 6,750 served | 8 | within |
| 12 | Va Medical Center Helena | Fort Harrison · 1,275 served | 7 | within |
Most EPA Violations in Montana
Community water systems in Montana with the most health-based EPA Safe Drinking Water Act violations on record. A health-based violation means a contaminant exceeded its federal limit or required treatment was not applied.
| # | Water System | Location | Health-based violations |
|---|---|---|---|
| 1 | Whitehall Town Of | Whitehall · 1,500 served | 43 |
| 2 | Philipsburg Town Of | Philipsburg · 1,360 served | 19 |
| 3 | Libby City Of | Libby · 4,892 served | 6 |
| 4 | Virginia City Water Dept | Virginia City · 1,500 served | 5 |
| 5 | Great Falls City Of | Great Falls · 60,000 served | 5 |
| 6 | Black Eagle Cascade County Water Sewer | Black Eagle · 1,233 served | 4 |
| 7 | Chinook City Of | Chinook · 1,300 served | 4 |
| 8 | Miles City City Of | Miles City · 9,565 served | 3 |
| 9 | Helena Water System | Helena · 32,091 served | 3 |
| 10 | Malmstrom Air Force Base | Malmstrom Air Force Base · 8,850 served | 2 |
| 11 | Boulder City Of | Boulder · 1,400 served | 2 |
| 12 | Colstrip City Of | Colstrip · 2,350 served | 2 |
How This Report Card Is Built
PFAS rankings use EPA UCMR5 monitoring (2023-2025), showing each system's peak detection above the 4 ppt EPA limit. Lead rankings use the EPA Lead and Copper Rule 90th-percentile tap results. Violation counts come from the EPA Safe Drinking Water Information System (SDWIS) and count health-based violations. Lead and violation lists are limited to community water systems serving 1,000 or more people. Figures are the most severe on record and do not necessarily reflect current treated water.
Frequently Asked Questions
What is the most PFAS-contaminated water system in Montana?
In EPA UCMR5 testing (2023-2025), Malmstrom Air Force Base in Malmstrom Air Force Base had the highest recorded PFAS level in Montana at 7 ppt - about 2x the EPA's 4 ppt limit for PFOA and PFOS.
Which Montana water system has the highest lead levels?
Big Mountain Water Company in Whitefish had the highest 90th-percentile lead result in Montana under the EPA Lead and Copper Rule at 56 ppb - 3.7x the 15 ppb action level.
Which Montana water system has the most EPA violations?
Whitehall Town Of in Whitehall has the most health-based EPA Safe Drinking Water Act violations on record in Montana, with 43 violations.
Where does the Montana water report card data come from?
PFAS figures come from EPA UCMR5 monitoring (2023-2025), lead from the EPA Lead and Copper Rule 90th-percentile tap results, and violations from EPA SDWIS health-based violation records. Figures are the most severe on record and do not necessarily reflect current treated water. Check your exact address at knowyourexposure.com.
What Montana Residents Should Do
- Look up your exact address at knowyourexposure.com for your system's data
- See the full Montana water quality overview
- If your system is listed, a certified filter (reverse osmosis for PFAS, NSF-53 for lead) reduces exposure at the tap. See the best water filters.