All 34 systems had enough required samples to calculate a yearly average. 0 had at least one yearly average at or above a study benchmark; 34 did not.
EPA-based study benchmark: the unrounded cutoff this research uses to reproduce EPA’s January 2026 technical-assistance classification around the April 2024 federal levels. It is not a current standard or compliance finding and cannot determine household exposure or health risk.
Find your water system
ZIP codes are used only to route visitors to public water systems that reported serving them. Confirm the actual provider using a water bill or utility record.
System counts in Montana
Each count shows how many included water systems had a yearly average at or above the named study benchmark.
| Study benchmark | Systems at or above benchmark | Water systems included | Percent |
|---|---|---|---|
| PFOA: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 0 | 34 | 0.0% |
| PFOS: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 0 | 34 | 0.0% |
| PFHxS: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 34 | 0.0% |
| PFNA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 34 | 0.0% |
| HFPO-DA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 34 | 0.0% |
| Hazard Index: 1.5 study benchmark with at least two detected components (reproduces EPA classification around 1) | 0 | 34 | 0.0% |
Community water systems with complete monitoring
“Complete monitoring” means at least one sampling location had all required samples needed for a yearly average. Each PWSID appears once, preventing double counting across ZIP associations.
| Public water system | PWSID | Population served | Primary source | Sampling locations | Study benchmark result |
|---|---|---|---|---|---|
| ALPINE VILLAGE WUA | MT0003229 | 125 | Ground water | 1 | Below all study benchmarks |
| ANACONDA WATER DEPARTMENT | MT0000016 | 6,750 | Ground water | 1 | Below all study benchmarks |
| BELGRADE CITY OF | MT0000136 | 10,460 | Ground water | 7 | Below all study benchmarks |
| BIG PINES TRAILER COURT | MT0000450 | 78 | Ground water | 1 | Below all study benchmarks |
| BIG SKY COUNTY WATER AND SEWER DIST 363 | MT0002385 | 4,132 | Ground water | 2 | Below all study benchmarks |
| BILLINGS CITY OF | MT0000153 | 114,000 | Surface water | 1 | Below all study benchmarks |
| BLACK ROCK ESTATES SUBDIVISION | MT0004881 | 75 | Ground water | 1 | Below all study benchmarks |
| BOZEMAN CITY OF | MT0000161 | 56,000 | Surface water | 2 | Below all study benchmarks |
| BUTTE SILVERBOW WATER DEPT | MT0000170 | 33,000 | Surface water | 3 | Below all study benchmarks |
| COLUMBIA FALLS CITY OF | MT0000181 | 4,450 | Ground water | 1 | Below all study benchmarks |
| DILLON CITY OF | MT0000201 | 4,300 | Ground water | 3 | Below all study benchmarks |
| FAIRFIELD TOWN OF | MT0000212 | 718 | Ground water | 5 | Below all study benchmarks |
| FLATHEAD COUNTY WATER AND SEWER | MT0001744 | 7,775 | Ground water | 4 | Below all study benchmarks |
| GREAT FALLS CITY OF | MT0000525 | 60,000 | Surface water | 1 | Below all study benchmarks |
| HAMILTON CITY OF | MT0000234 | 5,660 | Ground water | 4 | Below all study benchmarks |
| HARDIN CITY OF | MT0000235 | 3,500 | Surface water | 1 | Below all study benchmarks |
| HAVRE CITY OF | MT0000524 | 9,921 | Surface water | 1 | Below all study benchmarks |
| HELENA WATER SYSTEM | MT0000241 | 32,091 | Surface water | 3 | Below all study benchmarks |
| KALISPELL PUBLIC WORKS | MT0000259 | 25,000 | Ground water | 8 | Below all study benchmarks |
| LAUREL MUNICIPAL WATER SYSTEM | MT0000270 | 6,339 | Surface water | 1 | Below all study benchmarks |
| LEWISTOWN CITY OF | MT0000271 | 5,923 | Ground water | 1 | Below all study benchmarks |
| LIVINGSTON CITY OF | MT0000573 | 7,500 | Ground water | 6 | Below all study benchmarks |
| LOCKWOOD WATER AND SEWER DISTRICT | MT0000156 | 5,900 | Surface water | 1 | Below all study benchmarks |
| MALMSTROM AIR FORCE BASE | MT0000515 | 8,850 | Surface water purchased | 2 | Below all study benchmarks |
| MILES CITY CITY OF | MT0000291 | 9,565 | Surface water | 1 | Below all study benchmarks |
| MISSOULA WATER | MT0000294 | 68,200 | Ground water | 23 | Below all study benchmarks |
| PHANTOM HILLS WATER SYSTEM | MT0004379 | 810 | Ground water | 1 | Below all study benchmarks |
| PINESDALE TOWN OF | MT0002926 | 800 | Surface water | 3 | Below all study benchmarks |
| RIVER ROCK COUNTY WATER AND SEWER DIST | MT0004082 | 4,200 | Ground water | 1 | Below all study benchmarks |
| SHELBY CITY OF | MT0000328 | 3,970 | Ground water | 1 | Below all study benchmarks |
| SUN PRAIRIE VILLAGE COUNTY | MT0000521 | 1,800 | Ground water | 1 | Below all study benchmarks |
| TOWN OF BROWNING | 083090091 | 4,671 | Surface water purchased | 1 | Below all study benchmarks |
| WEST YELLOWSTONE TOWN OF | MT0003136 | 9,899 | Ground water | 3 | Below all study benchmarks |
| WHITEFISH CITY OF | MT0000357 | 10,418 | Surface water | 1 | Below all study benchmarks |
What is included
Each active community water system with enough required samples for a yearly average is counted once, even if it is linked with several ZIP codes. This does not mean every home was tested. Private wells are excluded, and UCMR 5 did not comprehensively monitor every small system. This page does not apply Montana's state-specific standards or determine compliance. Use the official state or territory drinking-water program for current regulatory information.