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Tap water quality report

Denison, IA

EPA monitoring detected 17 contaminants across the 2 water suppliers serving Denison. 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.

2
water suppliers
11,809
people served
17
contaminants found
Iowa rankings Lead in Iowa PFAS in Iowa

What was found in Denison'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
1300 µg/L 13%
of the EPA limit 10000 µg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
1/2 SYR4
Fluoride
800 µg/L 20%
of the EPA limit 4000 µg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2013
1/2 SYR4
TTHM
53.825 µg/L 67%
of the EPA limit 80 µg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
Highest in the city: 56.59999999999998 µg/L — W CENTRAL RWA - DENISON SUBSYS · 2,428 people · 2018
2/2 SYR4
Copper
46.61999999999996 µg/L 3.6%
of the EPA limit 1300 µg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
1/2 SYR4
Chloroform
34.4 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
2/2 SYR4
Barium
27.2 µg/L 1.4%
of the EPA limit 2000 µg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2013
1/2 SYR4
Total Haloacetic Acids (HAA5)
23.125 µg/L 39%
of the EPA limit 60 µg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
2/2 SYR4
Bromodichloromethane
10.975 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
Highest in the city: 16.699999999999996 µg/L — W CENTRAL RWA - DENISON SUBSYS · 2,428 people · 2018
2/2 SYR4
Dibromochloromethane
12.2 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
Highest in the city: 16.249999999999996 µg/L — W CENTRAL RWA - DENISON SUBSYS · 2,428 people · 2018
2/2 SYR4
Monochloroacetic Acid
14.969999999999992 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
1/2 SYR4
Lithium
14 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2025
1/2 UCMR-5
Dichloroacetic Acid
7.46 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
2/2 SYR4
Bromoform
4.9175 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
Highest in the city: 6.225 µg/L — W CENTRAL RWA - DENISON SUBSYS · 2,428 people · 2018
2/2 SYR4
Lead
5.2 µg/L 35%
of the EPA limit 15 µg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
1/2 SYR4
Dibromoacetic Acid
4.805000000000001 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
Highest in the city: 4.899999999999999 µg/L — W CENTRAL RWA - DENISON SUBSYS · 2,428 people · 2018
2/2 SYR4
Trichloroacetic Acid
1.6675 µg/L
No EPA limit set
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2019
Highest in the city: 1.8499999999999996 µg/L — W CENTRAL RWA - DENISON SUBSYS · 2,428 people · 2018
2/2 SYR4
Lead
0.0012 mg/L 8%
of the EPA limit 0.0150 mg/L
Main supplier: DENISON WATER SUPPLY · 9,381 people · 2025
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 Denison

SupplierPopulation served
DENISON WATER SUPPLY 9,381
W CENTRAL RWA - DENISON SUBSYS 2,428

Frequently asked questions about Denison tap water

Is Denison tap water safe to drink?

EPA testing detected 17 contaminants in the water serving Denison. 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 Denison?

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

What contaminants are in Denison's water?

The contaminants EPA monitoring detected in Denison include Nitrate, Fluoride, TTHM, Copper, 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.