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 |
|---|---|---|---|---|
|
Highland Water District Snohomish County |
3,121 | 2 | 0 | |
|
Surfside Homeowners Pacific County |
2,687 | 2 | 0 | |
|
Jackson Park Naval Hospital Kitsap County |
2,277 | 1 | 0 | |
|
Kopachuck Middle & Voyager Elem WS Pierce County |
1,150 | 2 | 0 | |
|
Scatchet Head Water District Island County |
900 | 2 | 0 | |
|
Rolling Hills-Glencairn Island County |
872 | 4 | 0 | |
|
Packaging Corporation of America Walla Walla County |
700 | 1 | 0 | |
|
Penn Cove Water and Sewer District Island County |
460 | 1 | 0 | |
|
Silver Lake Water Island County |
425 | 1 | 0 | |
|
Whidbey West Water Assoc. Island County |
415 | 3 | 0 | |
|
Parker County |
300 | 4 | 0 | |
|
Shirona Water System Island County |
243 | 2 | 0 | |
|
Kittitas CO WD #2 Kittitas County |
242 | 2 | 1 | |
|
Arrowhead Beach Coop Water Assoc Island County |
168 | 1 | 0 | |
|
Orient Water Company Ferry County |
167 | 4 | 1 | |
|
Portland Fair Estates San Juan County |
130 | 3 | 0 | |
|
Devries Road Community Assn Island County |
76 | 3 | 0 | |
|
Norcliffe Water Association Island County |
57 | 3 | 0 | |
|
Beverly Beach Improvement Club Island County |
56 | 1 | 0 | |
|
Briarwood Water System Island County |
44 | 2 | 1 | |
|
Hannah Heights #2 Water Users Assn San Juan County |
44 | 2 | 0 | |
|
San Juan Fairways Owners Assn San Juan County |
40 | 2 | 0 | |
|
Lacey Water Department Thurston County |
105,178 | 1 | 0 | |
|
Parkland Light & Water Company Pierce County |
33,775 | 1 | 0 | |
|
Pullman Water Department City of Whitman County |
31,315 | 3 | 0 | |
|
Quil Ceda Village Tulalip · County |
30,000 | 4 | 0 | |
|
Fife Dept of Public Works Pierce County |
29,091 | 1 | 0 | |
|
Lake Meridian Water District King County |
24,231 | 1 | 0 | |
|
Oak Harbor City of Island County |
23,675 | 1 | 0 | |
|
Consolidated Irrig Dist 19 System 2 Spokane County |
21,220 | 1 | 0 | |
|
Sunnyside City of Yakima County |
17,194 | 4 | 1 | |
|
Toppenish Water Department Yakima County |
13,382 | 1 | 0 | |
|
Grandview City of Yakima County |
11,010 | 2 | 0 | |
|
Chelan Water Dept City of Chelan County |
9,425 | 2 | 0 | |
|
Port Angeles Composite Clallam County |
8,872 | 1 | 0 | |
|
Ephrata Water Department Grant County |
8,718 | 2 | 0 | |
|
Tulalip Bay Water Dist #1 Marysville · County |
5,968 | 1 | 0 | |
|
Wapato Waterworks Yakima County |
5,255 | 3 | 0 | |
|
Castle Rock Municipal Water Cowlitz County |
4,367 | 2 | 0 | |
|
Irvin Water District #6 Spokane County |
4,150 | 1 | 0 | |
|
Eatonville Water Dept Pierce County |
3,945 | 1 | 0 | |
|
Lummi Tribal Water District Ferndale · County |
3,699 | 8 | 3 | |
|
Roosevelt Water Association Snohomish County |
3,530 | 1 | 0 | |
|
Colfax Water Department City of Whitman County |
3,507 | 2 | 0 | |
|
Algona Water Dept King County |
3,300 | 1 | 0 | |
|
Nisqually-Leschi & West Nisqually Olympia · County |
3,200 | 7 | 0 | |
|
Gold Bar City of Snohomish County |
2,745 | 1 | 0 | |
|
Camano Water Association Island County |
2,592 | 1 | 0 | |
|
Badger Mountain Irrigation District Benton County |
2,331 | 2 | 0 | |
|
Angel of the Winds Arlington · County |
2,303 | 5 | 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.