What was found in Rancho Santa Margarita's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate-Nitrite | 430000 µg/L 4300% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2018 | 1/2 | SYR4 |
| Nitrate | 703 µg/L 7% of the EPA limit 10000 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Fluoride | 490 µg/L 12% of the EPA limit 4000 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Barium | 98.09 µg/L 4.9% of the EPA limit 2000 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| TTHM | 60.4 µg/L 76% of the EPA limit 80 µg/L Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Lithium | 50.1 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2025 | 1/2 | UCMR-5 |
| Total Haloacetic Acids (HAA5) | 23.628 µg/L 39% of the EPA limit 60 µg/L Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Chloroform | 20.575 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Bromodichloromethane | 18.4 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Dibromochloromethane | 18.05 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Arsenic | 16.84 µg/L 168% of the EPA limit, at the 95th percentile of samples — 10 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Gross Beta Particle Activity | 14.925 pCi/L No EPA limit set Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Dichloroacetic Acid | 12.9 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Selenium | 11.1 µg/L 22% of the EPA limit 50 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Dichloromethane | 9.82 µg/L 196% of the EPA limit, at the 95th percentile of samples — 5 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Antimony, Total | 9.53 µg/L 159% of the EPA limit, at the 95th percentile of samples — 6 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Trichloroacetic Acid | 7.75 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 1/2 | SYR4 |
| Bromoform | 7.1 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Combined Uranium | 6.02705 µg/L 20% of the EPA limit 30 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Dibromoacetic Acid | 4.82 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 2/2 | SYR4 |
| Copper | 3.56 µg/L 0.3% of the EPA limit 1300 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Toluene | 2.7 µg/L 0.3% of the EPA limit 1000 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Monobromoacetic Acid | 1.8 µg/L No EPA limit set Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2019 | 1/2 | SYR4 |
| Xylenes, Total | 1.1 µg/L 0% of the EPA limit 10000 µg/L Highest in the city: SMWD - SJ GROUND WATER PLANT · 0 people · 2019 | 1/2 | SYR4 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: SANTA MARGARITA WATER DISTRICT · 168,289 people · 2024 | 1/2 | LCR |
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 the
system's samples — over 100% is worth reading, but is not by itself a
violation.
Formal violations are listed separately.
These are the utilities' own EPA-reported results, not a city-wide
average. A detection means the lab measured the
substance — it isn't the same as exceeding a legal limit. Hover a source
tag to see the EPA program and years behind each figure.
Water suppliers serving Rancho Santa Margarita
| Supplier | Population served |
|---|---|
| SANTA MARGARITA WATER DISTRICT | 168,289 |
| SMWD - SJ GROUND WATER PLANT | 0 |
Frequently asked questions about Rancho Santa Margarita tap water
Is Rancho Santa Margarita tap water safe to drink?
EPA testing detected 25 contaminants in the water serving Rancho Santa Margarita. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve Rancho Santa Margarita?
2 public water suppliers report drinking-water monitoring for Rancho Santa Margarita, California to the EPA. Each is listed above with its population served.
What contaminants are in Rancho Santa Margarita's water?
The contaminants EPA monitoring detected in Rancho Santa Margarita include Nitrate-Nitrite, Nitrate, Fluoride, Barium, TTHM. The full list, with the level at the main supplier and the data source, is in the table above.
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.