TTHM (Total Trihalomethanes) violations in Washington
212 active public water systems in Washington had a TTHM (Total Trihalomethanes) violation in the past three years, 22 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 |
|---|---|---|---|---|
|
Shelter Bay Community INC Skagit County |
2,212 | 3 | 1 | |
|
Suquamish Regional Public Water System Poulsbo · County |
1,874 | 5 | 0 | |
|
Maxwelton Water System Island County |
1,700 | 3 | 0 | |
|
Lucky Eagle Casino Oakville · County |
1,550 | 5 | 3 | |
|
Port Gamble Sklallam Port Gamble · County |
1,509 | 1 | 0 | |
|
Port Susan Camp Club #1 Marysville · County |
1,500 | 2 | 0 | |
|
Squaxin Consolidated Shelton · County |
1,500 | 6 | 1 | |
|
Pelican Point by Cascadia LLC Grant County |
1,357 | 1 | 0 | |
|
Shorecrest Estates Water Co Mason County |
1,321 | 3 | 1 | |
|
Harrah Water System Yakima County |
1,304 | 1 | 0 | |
|
Makah Neah Bay Neah Bay · County |
1,300 | 11 | 0 | |
|
Lewis CO Water Dist #1 Lewis County |
1,174 | 1 | 0 | |
|
Boston Harbor Thurston County |
1,153 | 1 | 0 | |
|
Skokomish Skokomish Nation · County |
1,150 | 5 | 1 | |
|
Wilkeson Water Department Pierce County |
1,071 | 2 | 0 | |
|
Port Susan Camp Club #2 Marysville · County |
1,000 | 1 | 0 | |
|
Port Susan Camp Club #3 Marysville · County |
1,000 | 2 | 0 | |
|
Finley School District #53 Benton County |
990 | 4 | 0 | |
|
Odessa Lincoln County |
986 | 5 | 0 | |
|
Pioneer School District Mason County |
903 | 1 | 0 | |
|
Meridian School Complex Whatcom County |
900 | 1 | 0 | |
|
Carbonado Water Dept Pierce County |
875 | 1 | 0 | |
|
PE Ell Town of Lewis County |
859 | 4 | 0 | |
|
Camaloch Association Island County |
825 | 1 | 0 | |
|
Heritage University Water System Toppenish · County |
750 | 5 | 1 | |
|
Northgate Terrace Community Club Island County |
750 | 2 | 0 | |
|
Lost Lake Property Owners Assn Island County |
736 | 2 | 0 | |
|
Garfield Water Department Whitman County |
694 | 4 | 0 | |
|
McNeil Island Water Pierce County |
692 | 2 | 1 | |
|
Griffin School Thurston County |
672 | 1 | 0 | |
|
Vistaire Water System Island County |
647 | 2 | 0 | |
|
Chehalis Tribal Housing Oakville · County |
620 | 7 | 0 | |
|
McKenna Water District Pierce County |
600 | 2 | 0 | |
|
North Whidbey Water District Island County |
568 | 2 | 0 | |
|
Northwood Casino Lynden · County |
500 | 5 | 0 | |
|
Pasco Port of 210 Franklin County |
500 | 3 | 0 | |
|
Sunvista Sunlight Beach HOA Island County |
500 | 1 | 0 | |
|
Newaukum Hill Water Assn Lewis County |
493 | 2 | 0 | |
|
Dugualla Community INC Island County |
459 | 4 | 0 | |
|
Black Diamond Water District Clallam County |
452 | 3 | 0 | |
|
Doe Bay Water Users Assoc San Juan County |
442 | 1 | 0 | |
|
Combined Water System Island County |
435 | 2 | 0 | |
|
Crosswoods Water System Island County |
420 | 1 | 0 | |
|
Resort and Marina Clallam County |
409 | 4 | 0 | |
|
Nooksack Market Deming · County |
400 | 5 | 0 | |
|
Sierra Country Club Island County |
400 | 1 | 0 | |
|
Omak Hud Nespelem · County |
380 | 9 | 0 | |
|
Sun Mountain Resort Okanogan County |
376 | 2 | 0 | |
|
Cuyamaca Olympia · County |
375 | 7 | 0 | |
|
Keller Mallott · County |
340 | 10 | 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 Washington 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.