TTHM (Total Trihalomethanes) violations in Montana
87 active public water systems in Montana had a TTHM (Total Trihalomethanes) violation in the past three years, 5 of them in the latest quarter of EPA's data. What TTHM (Total Trihalomethanes) is and why it matters.
Systems with a TTHM (Total Trihalomethanes) violation
Latest quarter first, then largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Fort Belknap Agency Water System County |
2,600 | 3 | 0 | |
|
Harlem City of Harlem · Blaine County |
820 | 5 | 1 | |
|
Hillside Village Billings · Yellowstone County |
650 | 3 | 1 | |
|
Richland CO Valley View Wua Sidney · Richland County |
85 | 3 | 1 | |
|
Hartland Colony Havre · Blaine County |
73 | 5 | 1 | |
|
Butte Silverbow Water Dept Butte · Silver Bow County |
33,000 | 2 | 0 | |
|
Billings Heights CO Water Dist of Billings · Yellowstone County |
12,000 | 3 | 0 | |
|
Malmstrom Air Force Base Great Falls · Cascade County |
8,850 | 3 | 0 | |
|
River Rock County Water and Sewer Dist Belgrade · Gallatin County |
4,200 | 2 | 0 | |
|
Hardin City of Hardin · Big Horn County |
3,500 | 1 | 0 | |
|
Poplar, City of County |
3,025 | 5 | 2 | |
|
Dry Prairie Rural Water Authority Culbertson · Roosevelt County |
3,005 | 2 | 0 | |
|
Colstrip City of Colstrip · Rosebud County |
2,350 | 2 | 0 | |
|
Assiniboine & Sioux Rural Water System County |
1,726 | 1 | 0 | |
|
Plains Town of Plains · Sanders County |
1,700 | 1 | 0 | |
|
Boulder City of Boulder · Jefferson County |
1,400 | 2 | 1 | |
|
Fairview Town of Fairview · Richland County |
1,000 | 2 | 0 | |
|
Shepherd Schools Shepherd · Yellowstone County |
800 | 3 | 1 | |
|
Montana State Hospital Complex Warm Springs · Deer Lodge County |
721 | 5 | 1 | |
|
North Star Pud Helena · Lewis and Clark County |
715 | 2 | 0 | |
|
ST Labre Indian School Ashland · Rosebud County |
650 | 3 | 0 | |
|
Circle Town of Circle · McCone County |
644 | 3 | 0 | |
|
Cherry Creek Estates LLC Billings · Yellowstone County |
600 | 2 | 1 | |
|
Covered Wagon MB HM Park Bozeman · Gallatin County |
500 | 1 | 0 | |
|
Fromberg Town of Fromberg · Carbon County |
498 | 5 | 1 | |
|
Cut Bank North Water District Santa Rita · Glacier County |
478 | 3 | 0 | |
|
Tri County Water District Fairfield · Teton County |
470 | 3 | 1 | |
|
Frazer Water System County |
452 | 2 | 0 | |
|
Consolidated Charlo Lake CO W and S Dist Charlo · Lake County |
450 | 2 | 0 | |
|
North Valley County Water and Sewer Dist St Marie · Valley County |
450 | 5 | 2 | |
|
Pryor Water System County |
406 | 7 | 1 | |
|
Eagleman Community Water County |
400 | 3 | 0 | |
|
Brockton, Town of County |
375 | 1 | 0 | |
|
Jordan Town of Jordan · Garfield County |
364 | 5 | 1 | |
|
Dutton Town of Dutton · Teton County |
338 | 6 | 0 | |
|
Paws UP Angus Ranch Main Complex Greenough · Missoula County |
327 | 3 | 0 | |
|
Mountain Acres MB HM PK Lewistown · Fergus County |
320 | 2 | 0 | |
|
Nashua Town of Nashua · Valley County |
300 | 3 | 1 | |
|
Seville Water System County |
300 | 5 | 0 | |
|
Lame Deer High School County |
291 | 5 | 2 | |
|
Wyola Water System County |
281 | 10 | 1 | |
|
Trapper Creek Job Corps Darby · Ravalli County |
275 | 4 | 0 | |
|
Ryegate Town of Ryegate · Golden Valley County |
270 | 3 | 0 | |
|
Hysham Town of Hysham · Treasure County |
262 | 4 | 0 | |
|
Heart Butte School County |
250 | 5 | 4 | |
|
Helena RV and Mobile Home Park Helena · Lewis and Clark County |
250 | 1 | 0 | |
|
Ryan Dam Water System Great Falls · Cascade County |
230 | 1 | 0 | |
|
Casitas del Rio Glendive · Dawson County |
216 | 4 | 0 | |
|
Pretty Eagle School County |
188 | 3 | 0 | |
|
Winnett Town of Winnett · Petroleum County |
187 | 8 | 1 |
About this data
A system is counted once if any of its violations in the past three years involved TTHM (Total Trihalomethanes), including monitoring and reporting lapses. Rules violated and status in the table are for the whole system, not TTHM (Total Trihalomethanes) alone.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The Montana records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet.