TTHM (Total Trihalomethanes) violations in Illinois
355 active public water systems in Illinois had a TTHM (Total Trihalomethanes) violation in the past three years, 50 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 |
|---|---|---|---|---|
|
Willowbrook Willowbrook · DuPage County |
9,000 | 3 | 2 | |
|
Clear Water Service Corp Coles County |
8,900 | 2 | 0 | |
|
Olney Olney · Richland County |
8,877 | 1 | 0 | |
|
Lake Villa Lake Villa · Lake County |
8,829 | 1 | 0 | |
|
Calumet Park Calumet Park · Cook County |
8,442 | 3 | 2 | |
|
Crete Crete · Will County |
8,386 | 4 | 0 | |
|
Benton Benton · Franklin County |
8,104 | 5 | 1 | |
|
Fosterburg Pwd Madison County |
7,940 | 2 | 0 | |
|
Broadview Broadview · Cook County |
7,847 | 4 | 3 | |
|
Rock Island Arsenal, US Army Rock Island County |
7,800 | 2 | 0 | |
|
Duquoin Du Quoin · Perry County |
7,169 | 6 | 2 | |
|
Raccoon Water Company Marion County |
7,080 | 1 | 0 | |
|
Stickney Stickney · Cook County |
6,902 | 2 | 0 | |
|
Chillicothe Chillicothe · Peoria County |
6,660 | 5 | 0 | |
|
Winthrop Harbor Winthrop Harbor · Lake County |
6,565 | 4 | 3 | |
|
Carterville Carterville · Williamson County |
6,528 | 2 | 0 | |
|
Countryside Countryside · Cook County |
6,420 | 1 | 0 | |
|
Dallas Rural Water District Dallas City · Henderson County |
6,370 | 2 | 0 | |
|
Williamsville Williamsville · Sangamon County |
6,198 | 1 | 0 | |
|
Beardstown Beardstown · Cass County |
5,951 | 1 | 0 | |
|
Mount Zion Mount Zion · Macon County |
5,833 | 1 | 0 | |
|
Pinckneyville Pinckneyville · Perry County |
5,804 | 4 | 0 | |
|
Robbins Robbins · Cook County |
5,415 | 6 | 3 | |
|
Mitchell Pwd Madison County |
5,253 | 1 | 0 | |
|
Flora Flora · Clay County |
5,233 | 1 | 0 | |
|
Brighton Brighton · Macoupin County |
5,041 | 3 | 0 | |
|
South Highway Pwd Jackson County |
4,972 | 3 | 0 | |
|
Anna Anna · Union County |
4,910 | 2 | 0 | |
|
Round Lake Park Round Lake Park · Lake County |
4,900 | 4 | 1 | |
|
Lawrenceville Lawrenceville · Lawrence County |
4,524 | 7 | 2 | |
|
Hillsboro Hillsboro · Montgomery County |
4,402 | 3 | 0 | |
|
Woodhaven Lee County |
4,100 | 2 | 1 | |
|
Coal Valley Pwd Williamson County |
4,023 | 1 | 0 | |
|
Burnham Burnham · Cook County |
3,989 | 7 | 3 | |
|
Riverwoods Riverwoods · Lake County |
3,618 | 1 | 0 | |
|
Three County Pwd Madison County |
3,575 | 2 | 0 | |
|
South Jacksonville South Jacksonville · Morgan County |
3,501 | 4 | 0 | |
|
Oregon Oregon · Ogle County |
3,449 | 4 | 1 | |
|
Lutheran General Hospital Cook County |
3,400 | 6 | 1 | |
|
Carlyle Carlyle · Clinton County |
3,373 | 4 | 1 | |
|
Galena Galena · Jo Daviess County |
3,308 | 4 | 1 | |
|
Sleepy Hollow Sleepy Hollow · Kane County |
3,100 | 1 | 0 | |
|
West Prairie Water Company Douglas County |
3,073 | 1 | 0 | |
|
Christopher Christopher · Franklin County |
3,072 | 2 | 0 | |
|
Lakeside Pwd Jackson County |
3,065 | 4 | 0 | |
|
Marquette Heights Marquette Heights · Tazewell County |
2,974 | 2 | 0 | |
|
Arcola Arcola · Douglas County |
2,927 | 4 | 0 | |
|
McLeansboro Mcleansboro · Hamilton County |
2,812 | 5 | 4 | |
|
Fox Lake Hills Subdivision Lake CO PW Lake County |
2,628 | 1 | 0 | |
|
Bridgeport Bridgeport · Lawrence County |
2,572 | 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 Illinois 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.