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 |
|---|---|---|---|---|
|
Leisure Acres Water Association Island County |
35 | 3 | 0 | |
|
Meadowbrook Homeowners Assn Snohomish County |
35 | 1 | 0 | |
|
Bayview Meadows Water System Island County |
34 | 2 | 0 | |
|
Reservoir Hill Maintenance Assn Kittitas County |
34 | 3 | 0 | |
|
Sunrise Point Water CO Island County |
32 | 1 | 0 | |
|
Stillaguamish Natural Resources Arlington · County |
31 | 3 | 1 | |
|
Mountain Ridge Kittitas County |
28 | 2 | 0 | |
|
North Forty Property Owners Assn San Juan County |
27 | 1 | 0 | |
|
Cascade View Road Water System Island County |
26 | 2 | 0 | |
|
Ocosta Mobile Home Park LLC Grays Harbor County |
26 | 4 | 1 | |
|
Red Gate Mobile Home Park Pierce County |
25 | 5 | 0 | |
|
Woods Creek Water District Snohomish County |
25 | 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 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.