Tapcensus

TTHM (Total Trihalomethanes) violations in Louisiana

102 active public water systems in Louisiana had a TTHM (Total Trihalomethanes) violation in the past three years, 48 of them in the latest quarter of EPA's data. What TTHM (Total Trihalomethanes) is and why it matters.

Health effects: Long-term exposure is associated with increased bladder cancer risk. Some studies link high TTHM exposure to adverse reproductive outcomes. Bromodichloromethane is classified as a possible human carcinogen.

Systems with a TTHM (Total Trihalomethanes) violation

Latest quarter first, then largest first
SystemServesStatusRules violated, 3 yrUnresolved
Southwest Ouachita Waterworks, INC
Ouachita County
10,725 1 0
Parish Utilities of Ascension
Ascension County
9,732 2 1
Water & Sewer Commission 4 of ST Mary
St. Mary County
9,709 1 0
City of Franklin Water Supply
St. Mary County
8,325 5 2
City of Mansfield Water System
De Soto County
7,512 2 0
Ebarb Wwks Dist # 1 Aimwell Area
Sabine County
6,738 3 1
Cadeville Water District
Ouachita County
6,219 2 1
South Toledo Bend Water District
Sabine County
5,943 2 0
Town of Greenwood Water System
Caddo County
5,205 2 0
Keatchie Water System
De Soto County
4,446 6 4
Town of Ferriday Water System
Concordia County
3,816 6 2
Cameron Parish WW District 11-Sweet Lake
Cameron County
3,675 1 0
River Road Water System
Richland County
3,513 3 1
Culbertson Water System
Lincoln County
3,300 1 0
Darbonne WS North
Union County
3,186 1 1
Cameron Parish Water and WW District 1
Cameron County
3,096 1 0
East Allen Parish Water Works
Allen County
3,030 2 1
Town of Gramercy Waterworks
St. James County
2,860 2 0
Pendleton Water Association
Sabine County
2,634 6 1
Town of Zwolle Water System
Sabine County
2,520 4 1
Town of Simmesport Water System
Avoyelles County
2,142 4 0
Lake ST John Waterworks District 1
Concordia County
2,067 2 0
Tannehill Water System
Winn County
1,932 2 0
Blocker Water System
Webster County
1,719 2 0
Village of Chatham Water System
Jackson County
1,557 3 0
Village of Grayson Water System
Caldwell County
1,461 5 2
Holum Water System
Caldwell County
1,230 2 1
Southwest Avoyelles Water District
Avoyelles County
1,053 6 4
Hagewood Water System
Natchitoches County
1,017 2 0
Village of Pleasant Hill Water System
Sabine County
990 4 1
Village of Grosse Tete Water System
Iberville County
954 3 1
Pointe a la Hache Water System
Plaquemines County
882 3 1
Cameron Parish WW District 9
Cameron County
871 1 0
Marathon Petroleum Company LLC
St. John the Baptist County
817 3 0
Village of Rosedale Water System
Iberville County
664 3 2
Village of Calvin Water System
Winn County
591 5 2
Cameron Parish WW District 7
Cameron County
576 2 0
Hickory Grove Water System
Red River County
570 5 2
Lincoln Parish Waterworks District #1
Lincoln County
570 1 0
Village of Converse Water System
Sabine County
561 1 0
Village of Noble Water System
Sabine County
549 6 2
ST Landry Wwd 3 Port Barre Area B
St. Landry County
516 1 0
Spillway Estates Water System
Jackson County
501 2 0
Joyce Water Supply
Winn County
474 1 0
Village of Saline Water System
Bienville County
450 4 1
Port of West ST Mary
St. Mary County
400 2 1
Village of Bonita Water System
Morehouse County
360 5 3
ST Marys Water System
Bossier County
294 6 4
Village of Downsville Water System
Union County
216 2 0
Magnolia-Peg Leg Cove
Sabine County
189 1 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 Louisiana 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.