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 |
|---|---|---|---|---|
|
Hoving Business Center Helena · Lewis and Clark County |
170 | 5 | 1 | |
|
New Rockport Colony INC Choteau · Teton County |
160 | 2 | 0 | |
|
Lambert Sewer and Water Assn Lambert · Richland County |
150 | 4 | 0 | |
|
Brady County Water Sewer District Brady · Pondera County |
144 | 2 | 0 | |
|
Ncmrwa Pondera CO Service Area Conrad · Pondera County |
144 | 1 | 0 | |
|
Seville Colony Cut Bank · Glacier County |
116 | 1 | 0 | |
|
Savage Public School Savage · Richland County |
114 | 2 | 0 | |
|
Roy Water and Sewer District Roy · Fergus County |
110 | 2 | 0 | |
|
Grass Range Town of Grass Range · Fergus County |
102 | 4 | 0 | |
|
Harrison School District NO 23 Harrison · Madison County |
100 | 3 | 0 | |
|
Sweetgrass Water Users Assn Sweetgrass · Toole County |
100 | 3 | 1 | |
|
Tri Hil Wua Gore Hill Great Falls · Cascade County |
100 | 3 | 1 | |
|
Ramsay Water and Sewer District Ramsay · Silver Bow County |
97 | 3 | 0 | |
|
Peks Mobile Home Court Billings · Yellowstone County |
95 | 3 | 0 | |
|
Piegan Border Station Babb · Glacier County |
94 | 3 | 0 | |
|
Galen Facility Anaconda · Deer Lodge County |
90 | 3 | 0 | |
|
Greenfield Elem School Dist 75 Fairfield · Teton County |
90 | 5 | 0 | |
|
Ncmrwa North Havre Cwd Leg Havre · Hill County |
90 | 2 | 0 | |
|
West Glacier Wua West Glacier · Flathead County |
90 | 1 | 0 | |
|
Park Evergreen Trailer Court Helena · Lewis and Clark County |
87 | 2 | 0 | |
|
Flaxville Town of Flaxville · Daniels County |
82 | 4 | 1 | |
|
Absaloka Mine Hardin · Big Horn County |
80 | 2 | 0 | |
|
Prairie Community Hospital Terry · Prairie County |
80 | 2 | 0 | |
|
Rau School District NO 21 Sidney · Richland County |
80 | 3 | 2 | |
|
Bozeman Fish Technology Ctr Bozeman · Gallatin County |
75 | 2 | 0 | |
|
Swlo and Main Office Missoula · Missoula County |
75 | 7 | 0 | |
|
Duck Creek Mobile Home Park Billings · Yellowstone County |
70 | 5 | 0 | |
|
Milford Colony INC Wolf Creek · Lewis and Clark County |
67 | 7 | 0 | |
|
Blue Cloud Subdivision Helena · Lewis and Clark County |
60 | 1 | 0 | |
|
Water Resources Division Missoula · Missoula County |
60 | 8 | 1 | |
|
Antelope County Water and Sewer Antelope · Sheridan County |
59 | 3 | 0 | |
|
Kicking Horse Job Corps County |
54 | 1 | 0 | |
|
Hawarden Square Butte Water Fort Benton · Chouteau County |
50 | 2 | 1 | |
|
Pinnacle Estates of Glendive Glendive · Dawson County |
50 | 1 | 0 | |
|
Red Cliff Estates HOA Clancy · Jefferson County |
48 | 2 | 0 | |
|
Broadwater Estates HOA Helena · Lewis and Clark County |
40 | 2 | 0 | |
|
Mobile City 3 Helena · Lewis and Clark County |
40 | 4 | 0 |
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.