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Tap water quality report

Longmont, CO

EPA monitoring detected 15 contaminants across the 4 water suppliers serving Longmont. A detection doesn't automatically mean the water is unsafe — see the highest level found for each below, with its EPA source and period.

4
water suppliers
108,697
people served
15
contaminants found
Colorado rankings Lead in Colorado PFAS in Colorado

What was found in Longmont's water

The highest level seen across the city's suppliers, the EPA limit for each, and where the figure comes from.

ContaminantLevel vs EPA limitSuppliersSource
Fluoride
680 µg/L 17%
of the EPA limit 4000 µg/L
 2/4 SYR4
Nitrate
110 µg/L 1.1%
of the EPA limit 10000 µg/L
 2/4 SYR4
Nitrate-Nitrite
100 µg/L 1%
of the EPA limit 10000 µg/L
 2/4 SYR4
TTHM
69.4 µg/L 87%
of the EPA limit 80 µg/L
 2/4 SYR4
Total Haloacetic Acids (HAA5)
56.84 µg/L 95%
of the EPA limit 60 µg/L
 2/4 SYR4
Chloroform
40.9 µg/L
No EPA limit set
 2/4 SYR4
Barium
19 µg/L 1%
of the EPA limit 2000 µg/L
 2/4 SYR4
Trichloroacetic Acid
12.7 µg/L
No EPA limit set
 2/4 SYR4
Dichloroacetic Acid
9.54 µg/L
No EPA limit set
 2/4 SYR4
Bromodichloromethane
4.1 µg/L
No EPA limit set
 2/4 SYR4
Di(2-ethylhexyl) Phthalate
1.5 µg/L 25%
of the EPA limit 6 µg/L
 1/4 SYR4
Selenium
1 µg/L 2%
of the EPA limit 50 µg/L
 1/4 SYR4
Gross Alpha, Excl. Radon And U
0.6000 pCi/L 4%
of the EPA limit 15 pCi/L
 2/4 SYR4
Combined Radium (-226 And -228)
0.2000 pCi/L 4%
of the EPA limit 5 pCi/L
 1/4 SYR4
Lead
0.0020 mg/L 13%
of the EPA limit 0.0150 mg/L
 4/4 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 single worst sample on record — 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 Longmont

SupplierPopulation served
LONGMONT CITY OF 104,178
LONGS PEAK WD 3,200
COUNTRYSIDE OF LONGMONT 775
ST VRAIN MHP LLC 544

Frequently asked questions about Longmont tap water

Is Longmont tap water safe to drink?

EPA testing detected 15 contaminants in the water serving Longmont. 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 Longmont?

4 public water suppliers report drinking-water monitoring for Longmont, Colorado to the EPA. Each is listed above with its population served.

What contaminants are in Longmont's water?

The contaminants EPA monitoring detected in Longmont include Fluoride, Nitrate, Nitrate-Nitrite, TTHM, Total Haloacetic Acids (HAA5). The full list, with the highest level found 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.