What was found in Castle Rock'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 |
|---|---|---|---|
| Fluoride | 988 µg/L 25% of the EPA limit 4000 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 1527.5 µg/L — LOUVIERS WSD · 238 people · 2017 | 6/6 | SYR4 |
| Nitrate | 300 µg/L 3% of the EPA limit 10000 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 1300 µg/L — CONSOLIDATED BELL MTN RANCH MD · 1,162 people · 2019 | 5/6 | SYR4 |
| Nitrate-Nitrite | 310 µg/L 3.1% of the EPA limit 10000 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 400 µg/L — LOUVIERS WSD · 238 people · 2017 | 3/6 | SYR4 |
| Barium | 248.8 µg/L 12% of the EPA limit 2000 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 6/6 | SYR4 |
| Lithium | 25 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2024
Highest in the city: 30.9 µg/L — CASTLE PINES VILLAGE MD · 5,656 people · 2025 | 2/6 | UCMR-5 |
| Xylenes, Total | 26.315 µg/L 0.3% of the EPA limit 10000 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 1/6 | SYR4 |
| TTHM | 18.39 µg/L 23% of the EPA limit 80 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 5/6 | SYR4 |
| Gross Alpha, Excl. Radon And U | 7.02 pCi/L 47% of the EPA limit 15 pCi/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 13.0241 pCi/L — LOUVIERS WSD · 238 people · 2017 | 6/6 | SYR4 |
| Dibromochloromethane | 10.9195 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 5/6 | SYR4 |
| Combined Radium (-226 And -228) | 4.52 pCi/L 90% of the EPA limit 5 pCi/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 9.3 pCi/L — LOUVIERS WSD · 238 people · 2019 | 6/6 | SYR4 |
| Total Haloacetic Acids (HAA5) | 7.81 µg/L 13% of the EPA limit 60 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 4/6 | SYR4 |
| Gross Beta Particle Activity | 7 pCi/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2018 | 3/6 | SYR4 |
| Bromodichloromethane | 6.335 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 5/6 | SYR4 |
| Bromoform | 6.3 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 2/6 | SYR4 |
| Selenium | 4.5 µg/L 9% of the EPA limit 50 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 5/6 | SYR4 |
| Dibromoacetic Acid | 4.32 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 2/6 | SYR4 |
| Dichloroacetic Acid | 2.78 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 3.16 µg/L — CONSOLIDATED BELL MTN RANCH MD · 1,162 people · 2019 | 2/6 | SYR4 |
| Arsenic | 1.9 µg/L 19% of the EPA limit 10 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 3 µg/L — LOUVIERS WSD · 238 people · 2017 | 2/6 | SYR4 |
| Chromium | 2.7 µg/L 2.7% of the EPA limit 100 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019
Highest in the city: 3 µg/L — LOUVIERS WSD · 238 people · 2017 | 3/6 | SYR4 |
| Combined Uranium | 2.65 µg/L 8.8% of the EPA limit 30 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 3/6 | SYR4 |
| Chloroform | 2.405 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 5/6 | SYR4 |
| Ethylbenzene | 2.3 µg/L 0.3% of the EPA limit 700 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 1/6 | SYR4 |
| Monobromoacetic Acid | 2.16 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 1/6 | SYR4 |
| Thallium, Total | 2 µg/L 100% of the EPA limit 2 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 1/6 | SYR4 |
| Di(2-ethylhexyl) Phthalate | 1.9 µg/L 32% of the EPA limit 6 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 2/6 | SYR4 |
| Trichloroacetic Acid | 1.3 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 1/6 | SYR4 |
| Monochloroacetic Acid | 1.29 µg/L No EPA limit set Highest in the city: CONSOLIDATED BELL MTN RANCH MD · 1,162 people · 2019 | 1/6 | SYR4 |
| Picloram | 0.1000 µg/L 0% of the EPA limit 500 µg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2019 | 1/6 | SYR4 |
| Heptachlor | 0.0400 µg/L 10% of the EPA limit 0.4000 µg/L Highest in the city: LOUVIERS WSD · 238 people · 2019 | 1/6 | SYR4 |
| Pfba | 0.0051 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2024 | 1/6 | UCMR-5 |
| Pfpea | 0.0047 µg/L No EPA limit set Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2024 | 1/6 | UCMR-5 |
| Lead | 0.0020 mg/L 13% of the EPA limit 0.0150 mg/L Main supplier: CASTLE ROCK TOWN OF · 110,298 people · 2025
Highest in the city: 0.0030 mg/L — BEVERLY HILLS MUTUAL WC · 325 people · 2025 | 6/6 | 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 Castle Rock
| Supplier | Population served |
|---|---|
| CASTLE ROCK TOWN OF | 110,298 |
| CASTLE PINES VILLAGE MD | 5,656 |
| CONSOLIDATED BELL MTN RANCH MD | 1,162 |
| BEVERLY HILLS MUTUAL WC | 325 |
| SILVER HEIGHTS WSD | 301 |
| LOUVIERS WSD | 238 |
Frequently asked questions about Castle Rock tap water
Is Castle Rock tap water safe to drink?
EPA testing detected 32 contaminants in the water serving Castle Rock. 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 Castle Rock?
6 public water suppliers report drinking-water monitoring for Castle Rock, Colorado to the EPA. Each is listed above with its population served.
What contaminants are in Castle Rock's water?
The contaminants EPA monitoring detected in Castle Rock include Fluoride, Nitrate, Nitrate-Nitrite, Barium, Lithium. 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.