Total Trihalomethanes (TTHM)
Unresolved Total Trihalomethanes Rule violation cited in 2025 (total trihalomethanes (tthm)).
PWSID WA5302200 · Surface waterMunicipal
22,995 people served. No health-based SDWIS violations recorded in the past 5 years. 29 remain unresolved. Last cited 1 year ago.
Unresolved Total Trihalomethanes Rule violation cited in 2025 (total trihalomethanes (tthm)).
Unresolved Total Trihalomethanes Rule violation cited in 2025 (haloacetic acids (haa5)).
Unresolved Lead and Copper Rule violation cited in 2020 (contaminant 2210).
Unresolved Lead and Copper Rule violation cited in 2020 (contaminant 2214).
Health-based violations exceed an MCL or treatment-technique standard. Monitoring violations are reporting failures with no measured exceedance — they tell you the system isn't fully transparent, not that the water is unsafe today.
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Mount Vernon, Washington (Census place; block-group disparity scores aggregated by centroid containment): a service population of 35,120. Local disparity score for pm2.5 (fine particulate) sits well below the reference (37). Why we surface this →
Low-income
People of color
Under age 5
Over age 64
| Indicator | Disparity score | Reading |
|---|---|---|
| PM2.5 (fine particulate) | 37 | well below the reference |
| Ozone | 7 | well below the reference |
| Nitrogen dioxide (NO₂) | 40 | well below the reference |
| Diesel particulate | 56 | below the reference |
| Toxic releases (RSEI) | 45 | well below the reference |
| Traffic proximity | 60 | below the reference |
| Lead-paint risk (pre-1960 housing) | 53 | below the reference |
| Superfund site proximity | 0 | well below the reference |
| RMP-facility proximity | 103 | near the reference |
| Hazardous-waste site proximity | 60 | below the reference |
| Underground storage tanks | 94 | near the reference |
| NPDES wastewater proximity | 43 | well below the reference |
| Drinking-water non-compliance | 0 | well below the reference |
Source: Census ACS 2018-2022 (5-year) + USEPA-clone EJ blockgroup stats (raw indicators + EJ disparity mirror).
Source. EPA Safe Drinking Water Information System · retrieved 2026-05-07. Reporting period 2020-01-01 → 2026-05-07.
What this is not. SDWIS records compliance against federal MCLs — not a direct readout of tap-water concentrations. Active health-based violations are not the same as a current crisis; we link to the EPA record so you can verify return-to-compliance status before forming a conclusion.