Is Costa Mesa, CA Tap Water Safe? Quality & Contaminants

What was found in Costa Mesa'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	450 µg/L 4.5% of the EPA limit 10000 µg/L Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019 Highest in the city: 3000 µg/L — PINE VALLEY TRAILER PARK · 200 people · 2019	2/2	SYR4
Fluoride	517 µg/L 13% of the EPA limit 4000 µg/L Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Combined Uranium	214.786 µg/L 716% of the EPA limit, at the 95th percentile of samples — 30 µg/L Highest in the city: PINE VALLEY TRAILER PARK · 200 people · 2019	1/2	SYR4
TTHM	53.475 µg/L 67% of the EPA limit 80 µg/L Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Chloroform	35.68 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Total Haloacetic Acids (HAA5)	24.9 µg/L 42% of the EPA limit 60 µg/L Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Dichloroacetic Acid	12.85 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Bromodichloromethane	11.749 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Trichloroacetic Acid	9.965 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Gross Beta Particle Activity	7.7 pCi/L No EPA limit set Highest in the city: PINE VALLEY TRAILER PARK · 200 people · 2019	1/2	SYR4
Dibromochloromethane	4.9065 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Monochloroacetic Acid	3.4 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Bromoform	1.2 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Dibromoacetic Acid	1 µg/L No EPA limit set Main supplier: LAKE WOHLFORD RESORT · 250 people · 2019	1/2	SYR4
Lead	0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: LAKE WOHLFORD RESORT · 250 people · 2024	2/2	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 Costa Mesa

Supplier	Population served
LAKE WOHLFORD RESORT	250
PINE VALLEY TRAILER PARK	200

Frequently asked questions about Costa Mesa tap water

Is Costa Mesa tap water safe to drink?

EPA testing detected 15 contaminants in the water serving Costa Mesa. 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 Costa Mesa?

2 public water suppliers report drinking-water monitoring for Costa Mesa, California to the EPA. Each is listed above with its population served.

What contaminants are in Costa Mesa's water?

The contaminants EPA monitoring detected in Costa Mesa include Nitrate, Fluoride, Combined Uranium, TTHM, Chloroform. 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.