TTHM (Total Trihalomethanes) violations in Wisconsin
59 active public water systems in Wisconsin had a TTHM (Total Trihalomethanes) violation in the past three years, 3 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 |
|---|---|---|---|---|
|
Appleton Waterworks Menasha · Outagamie County |
74,511 | 3 | 1 | |
|
Bellevue Waterworks Green Bay · Brown County |
16,715 | 2 | 1 | |
|
Osseo Waterworks Osseo · Trempealeau County |
1,701 | 1 | 0 | |
|
Watertown Waterworks Watertown · Jefferson County |
23,945 | 1 | 0 | |
|
Grand Chute TN San Dist 1 Grand Chute · Outagamie County |
21,583 | 2 | 0 | |
|
Waunakee Waterworks Waunakee · Dane County |
14,879 | 1 | 0 | |
|
Greendale Waterworks Greendale · Milwaukee County |
14,393 | 1 | 0 | |
|
Port Washington Waterworks Port Washington · Ozaukee County |
12,853 | 1 | 0 | |
|
Ashland Water Utility Ashland · Ashland County |
8,000 | 3 | 0 | |
|
Lake Hallie Waterworks Village of Chippewa Falls · Chippewa County |
6,701 | 4 | 2 | |
|
Combined Locks Waterworks Combined Locks · Outagamie County |
3,609 | 3 | 1 | |
|
Sherwood Waterworks Sherwood · Calumet County |
3,114 | 4 | 1 | |
|
Genoa City Waterworks Genoa City · Walworth County |
2,766 | 2 | 0 | |
|
Lomira Waterworks Lomira · Dodge County |
2,701 | 4 | 1 | |
|
Somers Water Utility Somers · Kenosha County |
1,930 | 1 | 0 | |
|
Spencer Waterworks Spencer · Marathon County |
1,848 | 4 | 2 | |
|
New Odanah County |
1,839 | 5 | 0 | |
|
Shorewood Hills Waterworks Madison · Dane County |
1,670 | 3 | 1 | |
|
Stratford Waterworks Stratford · Marathon County |
1,643 | 3 | 1 | |
|
Hurley Waterworks Hurley · Iron County |
1,515 | 3 | 1 | |
|
Augusta Waterworks Augusta · Eau Claire County |
1,450 | 8 | 0 | |
|
Mole Lake County |
1,260 | 4 | 1 | |
|
Glenwood City Waterworks Glenwood City · St. Croix County |
1,102 | 1 | 0 | |
|
Athens Waterworks Athens · Marathon County |
1,025 | 3 | 1 | |
|
Albany Waterworks Albany · Green County |
1,018 | 2 | 0 | |
|
Southern Wisconsin Center Union Grove · Racine County |
950 | 4 | 0 | |
|
Elmwood Waterworks Elmwood · Pierce County |
798 | 4 | 2 | |
|
Iowa Grant Schools Livingston · Iowa County |
730 | 1 | 0 | |
|
Montfort Waterworks Montfort · Grant County |
718 | 3 | 2 | |
|
Rockland Waterworks Rockland · La Crosse County |
642 | 3 | 1 | |
|
Eleva Waterworks Eleva · Trempealeau County |
635 | 10 | 0 | |
|
Iron River Sanitary District Iron River · Bayfield County |
600 | 5 | 1 | |
|
Ontario Waterworks Ontario · Vernon County |
554 | 4 | 1 | |
|
Beaver Dam North Water Distribution System Beaver Dam · Dodge County |
550 | 2 | 1 | |
|
Melrose Waterworks Melrose · Jackson County |
524 | 1 | 0 | |
|
Clark County Rehabilitation & Living Center Owen · Clark County |
510 | 5 | 1 | |
|
Lakeview Specialty Hospital Waterford · Racine County |
484 | 9 | 2 | |
|
Cochrane Waterworks Cochrane · Buffalo County |
450 | 4 | 0 | |
|
Land O Lakes Sanitary Dist Land O Lakes · Vilas County |
450 | 6 | 0 | |
|
Hancock Waterworks Hancock · Waushara County |
419 | 5 | 1 | |
|
Cazenovia Waterworks Cazenovia · Richland County |
351 | 3 | 1 | |
|
Goodman Sanitary Dist NO 1 Goodman · Marinette County |
350 | 6 | 1 | |
|
Land O Lakes INC Cheese Div Spencer · Marathon County |
350 | 2 | 0 | |
|
Rainbow Lake Manor MHP Bristol · Kenosha County |
350 | 2 | 0 | |
|
Northernaire Sanitary District Three Lakes · Oneida County |
315 | 4 | 0 | |
|
Fifield Sanitary District Fifield · Price County |
300 | 3 | 2 | |
|
Butternut Waterworks Butternut · Ashland County |
283 | 6 | 3 | |
|
Sheldon Water Utility Sheldon · Rusk County |
265 | 6 | 1 | |
|
Browntown Waterworks Browntown · Green County |
256 | 7 | 1 | |
|
Westboro San Dist 1 Westboro · Taylor County |
150 | 3 | 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 Wisconsin 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.