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Tap water quality report

Half Moon Bay, CA

EPA monitoring detected 19 contaminants across the 1 water supplier serving Half Moon Bay. A detection doesn't automatically mean the water is unsafe — see the level at the main supplier for each below, with its EPA source and period.

1
water supplier
18,940
people served
19
contaminants found
California rankings Lead in California PFAS in California

What was found in Half Moon Bay'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.

ContaminantLevel vs EPA limitSuppliersSource
Nitrate
2215 µg/L 22%
of the EPA limit 10000 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Fluoride
883.5 µg/L 22%
of the EPA limit 4000 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
TTHM
90.5 µg/L 113%
of the EPA limit, at the 95th percentile of samples — 80 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Chloroform
45 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Barium
31.95 µg/L 1.6%
of the EPA limit 2000 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Bromodichloromethane
30 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Total Haloacetic Acids (HAA5)
30 µg/L 50%
of the EPA limit 60 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Dibromochloromethane
29.14999999999999 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Copper
23.19999999999999 µg/L 1.8%
of the EPA limit 1300 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Dichloroacetic Acid
15 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Trichloroacetic Acid
13.149999999999991 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Chromium
13.049999999999983 µg/L 13%
of the EPA limit 100 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Dibromoacetic Acid
9.725 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Bromoform
9.599999999999996 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Arsenic
8 µg/L 80%
of the EPA limit 10 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Di(2-ethylhexyl) Phthalate
3.2 µg/L 53%
of the EPA limit 6 µg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Monochloroacetic Acid
2.78 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Monobromoacetic Acid
1.185 µg/L
No EPA limit set
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2019
1/1 SYR4
Lead
0.0016 mg/L 11%
of the EPA limit 0.0150 mg/L
Main supplier: COASTSIDE COUNTY WATER DISTRICT · 18,940 people · 2024
1/1 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 Half Moon Bay

SupplierPopulation served
COASTSIDE COUNTY WATER DISTRICT 18,940

Frequently asked questions about Half Moon Bay tap water

Is Half Moon Bay tap water safe to drink?

EPA testing detected 19 contaminants in the water serving Half Moon Bay. 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 Half Moon Bay?

1 public water supplier report drinking-water monitoring for Half Moon Bay, California to the EPA. Each is listed above with its population served.

What contaminants are in Half Moon Bay's water?

The contaminants EPA monitoring detected in Half Moon Bay include Nitrate, Fluoride, TTHM, Chloroform, Barium. 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.