Compliance record
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.
| Contaminant | Level vs EPA limit | Detection rate | Source | Period |
|---|---|---|---|---|
| TTHM | 5.525 µg/L 6.9% of the EPA limit 80 µg/L
worst single sample: 21 µg/L | 40/40 | SYR4 | 2014–2019 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L | 35/35 | LCR | 2025 |
| Dibromochloromethane | 2.39 µg/L No EPA limit set
worst single sample: 8.3 µg/L | 28/40 | SYR4 | 2014–2019 |
| Bromoform | 1.8 µg/L No EPA limit set
worst single sample: 2.7 µg/L | 22/40 | SYR4 | 2014–2019 |
| Fluoride | 547.5 µg/L 14% of the EPA limit 4000 µg/L
worst single sample: 630 µg/L | 16/16 | SYR4 | 2012–2019 |
| Nitrate | 971.8 µg/L 9.7% of the EPA limit 10000 µg/L | 16/32 | SYR4 | 2012–2019 |
| Bromodichloromethane | 4.46 µg/L No EPA limit set
worst single sample: 6 µg/L | 8/40 | SYR4 | 2014–2019 |
| Total Haloacetic Acids (HAA5) | 21.49 µg/L 36% of the EPA limit 60 µg/L
worst single sample: 28 µg/L | 7/42 | SYR4 | 2013–2019 |
| Dibromoacetic Acid | 1.47 µg/L No EPA limit set
worst single sample: 1.5 µg/L | 4/42 | SYR4 | 2013–2019 |
| Combined Uranium | 6.3325 µg/L 21% of the EPA limit 30 µg/L
worst single sample: 6.407 µg/L | 3/3 | SYR4 | 2012–2019 |
| Dichloroacetic Acid | 16.37 µg/L No EPA limit set
worst single sample: 18 µg/L | 3/42 | SYR4 | 2013–2019 |
| Nitrate-Nitrite | 597000 µg/L 5970% of the EPA limit, at the 95th percentile of samples — 10000 µg/L
worst single sample: 600000 µg/L | 3/6 | SYR4 | 2012–2018 |
| Monobromoacetic Acid | 1.19 µg/L No EPA limit set
worst single sample: 1.2 µg/L | 2/42 | SYR4 | 2013–2019 |
| Trichloroacetic Acid | 9.655 µg/L No EPA limit set
worst single sample: 10 µg/L | 2/42 | SYR4 | 2013–2019 |
| Lithium | 42 µg/L No EPA limit set | 2/4 | UCMR-5 | 2024 |
| Chloroform | 4.2 µg/L No EPA limit set | 1/40 | SYR4 | 2014–2019 |
| Mercury | 1.2 µg/L 60% of the EPA limit 2 µg/L | 1/7 | SYR4 | 2012–2018 |
| Tetrachloroethylene | 0.6200 µg/L 12% of the EPA limit 5 µg/L | 1/18 | SYR4 | 2012–2019 |
63 contaminants tested, none detected
1,1,1-Trichloroethane1,1,2-Trichloroethane1,1-Dichloroethylene1,2,4-Trichlorobenzene1,2-Dichloroethane1,2-Dichloropropane11Cl-PF3OUdS4:2 Fts6:2 Fts8:2 Fts9Cl-PF3ONSAdonaAntimony, TotalArsenicBariumBenzeneBeryllium, TotalChlorobenzeneCopperCyanideCadmiumCarbon TetrachlorideChromiumDichloromethaneDi(2-ethylhexyl) PhthalateEthylbenzeneHfpo-DaLeadMonochloroacetic AcidNetfosaaNfdhaNmefosaaNitritePfbaPFBSPfdaPfdoaPfeesaPfhpaPfhpsPfhxaPFHXSPfmbaPfmpaPFNAPFOAPFOSPfpeaPfpesPftaPftrdaPfunaSeleniumStyreneThallium, TotalTolueneTrichloroethyleneVinyl ChlorideXylenes, Totalcis-1,2-DichloroethyleneO-DichlorobenzeneP-Dichlorobenzenetrans-1,2-Dichloroethylene
Utility contact
Frequently asked questions about Gswc - Willowbrook
Is Gswc - Willowbrook tap water safe to drink?
EPA monitoring detected 18 contaminants in Gswc - Willowbrook'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 Gswc - Willowbrook's water?
EPA monitoring detected TTHM, Lead, Dibromochloromethane, Bromoform, Fluoride, and others. The full list with the level and data source for each is above.
How many people does Gswc - Willowbrook serve?
Gswc - Willowbrook reports serving 10,793 people in California, per its EPA record.
Has Gswc - Willowbrook had any water quality violations?
The EPA has no formal drinking-water violations on file for Gswc - Willowbrook.
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.