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Tap water quality report

Mercer Island City of

EPA monitoring tested this supplier for 41 contaminants and detected 9. A detection doesn't automatically mean the water is unsafe — the level and EPA source for each is below.

41
contaminants tested
9
detected
31,057
people served
3
health-based violations
Washington rankingsLead in WashingtonPFAS in Washington
Water source
SWP
Ownership
Local government
Counties served
King

Compliance record

Formal violations the EPA has on file for this supplier. A health-based violation means a contaminant limit or a required treatment was breached; the rest are monitoring or reporting failures — still violations, but not a measured health risk.

3
health-based violations
6
violations on file
0
still open
ViolationTypeStatusPeriod
MCL Health-based Archived 1992-01-01 → 1992-01-31
MCL Health-based Archived 1992-01-01 → 1992-01-31
MCL Health-based Archived 1992-01-01 → 1992-01-31
MR Monitoring Archived 1992-12-01 → 1992-12-31
MR Monitoring Archived 1992-08-01 → 1992-08-31
MR Monitoring Archived 1992-05-01 → 1992-05-31

Other contaminants detected

Each bar shows the measured level as a share of the EPA limit: green is well under, amber is close to it, red is over. For lead and copper the limit applies to exactly the 90th-percentile figure shown, so red there means a real exceedance. For everything else the limit applies to a running annual average while the figure is the 95th percentile of this system's samples — over 100% is worth reading, but is not by itself a violation. Where a single sample came in higher than that percentile, it is noted under the bar. Formal violations are listed separately.
ContaminantLevel vs EPA limitDetection rateSourcePeriod
TTHM
47.8045 µg/L 60%
of the EPA limit 80 µg/L
worst single sample: 52.99 µg/L
112/112 SYR4 2012–2019
Total Haloacetic Acids (HAA5)
47.95 µg/L 80%
of the EPA limit 60 µg/L
worst single sample: 56.1 µg/L
111/111 SYR4 2012–2019
Chloroform
45.51 µg/L
No EPA limit set
worst single sample: 50.1 µg/L
110/110 SYR4 2012–2019
Dichloroacetic Acid
21.065 µg/L
No EPA limit set
worst single sample: 23.8 µg/L
110/110 SYR4 2012–2019
Bromodichloromethane
2.596 µg/L
No EPA limit set
worst single sample: 2.89 µg/L
107/107 SYR4 2012–2019
Trichloroacetic Acid
27.255 µg/L
No EPA limit set
worst single sample: 32.3 µg/L
104/104 SYR4 2012–2019
Monochloroacetic Acid
3.191 µg/L
No EPA limit set
worst single sample: 4.8 µg/L
30/111 SYR4 2012–2019
Bromoform
0.5000 µg/L
No EPA limit set
 1/112 SYR4 2012–2019
Dibromochloromethane
0.5500 µg/L
No EPA limit set
 1/111 SYR4 2012–2019
32 contaminants tested, none detected
11Cl-PF3OUdS4:2 Fts6:2 Fts8:2 Fts9Cl-PF3ONSAdonaDibromoacetic AcidHfpo-DaMonobromoacetic AcidNetfosaaNfdhaNmefosaaPfbaPFBSPfdaPfdoaPfeesaPfhpaPfhpsPfhxaPFHXSPfmbaPfmpaPFNAPFOAPFOSPfpeaPfpesPftaPftrdaPfunaLithium

Utility contact

Contact
Allen Hunter

Frequently asked questions about Mercer Island City of

Is Mercer Island City of tap water safe to drink?

EPA monitoring detected 9 contaminants in Mercer Island City of's water. A detection isn't the same as a violation — most levels are within federal limits. See each level and source above, and the utility's annual Consumer Confidence Report for its official compliance status.

What contaminants were detected in Mercer Island City of's water?

EPA monitoring detected TTHM, Total Haloacetic Acids (HAA5), Chloroform, Dichloroacetic Acid, Bromodichloromethane, and others. The full list with the level and data source for each is above.

How many people does Mercer Island City of serve?

Mercer Island City of reports serving 31,057 people in Washington, per its EPA record.

Has Mercer Island City of had any water quality violations?

The EPA has 6 violations on file for Mercer Island City of, of which 3 are health-based (a contaminant limit or required treatment was breached) and 0 remain open. The rest are monitoring or reporting failures.

Where does this data come from?

Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.