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Tap water quality report

Fort Thompson, SD

EPA monitoring detected 19 contaminants across the 3 water suppliers serving Fort Thompson. 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.

3
water suppliers
1,567
people served
19
contaminants found
South Dakota rankings Lead in South Dakota PFAS in South Dakota

What was found in Fort Thompson'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
Fluoride
1830 µg/L 46%
of the EPA limit 4000 µg/L
Highest in the city: BIG BEND WATER SYSTEM · 80 people · 2019
2/3 SYR4
Copper
751.5 µg/L 58%
of the EPA limit 1300 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
3/3 SYR4
Nitrate
200 µg/L 2%
of the EPA limit 10000 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
1/3 SYR4
Nitrate-Nitrite
90 µg/L 0.9%
of the EPA limit 10000 µg/L
Highest in the city: CROW CREEK SIOUX TRIBE WATER SYSTEM · 130 people · 2019
1/3 SYR4
Nitrite
90 µg/L 9%
of the EPA limit 1000 µg/L
Highest in the city: CROW CREEK SIOUX TRIBE WATER SYSTEM · 130 people · 2019
1/3 SYR4
TTHM
71.275 µg/L 89%
of the EPA limit 80 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
3/3 SYR4
Total Haloacetic Acids (HAA5)
63.725 µg/L 106%
of the EPA limit, at the 95th percentile of samples — 60 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
3/3 SYR4
Barium
34.02 µg/L 1.7%
of the EPA limit 2000 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
3/3 SYR4
Gross Alpha, Excl. Radon And U
4.585 pCi/L 31%
of the EPA limit 15 pCi/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
3/3 SYR4
Arsenic
2 µg/L 20%
of the EPA limit 10 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
Highest in the city: 3.9 µg/L — CROW CREEK SIOUX TRIBE WATER SYSTEM · 130 people · 2019
2/3 SYR4
Chromium
0.9660 µg/L 1%
of the EPA limit 100 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
Highest in the city: 3.7 µg/L — CROW CREEK SIOUX TRIBE WATER SYSTEM · 130 people · 2019
3/3 SYR4
Selenium
2.75 µg/L 5.5%
of the EPA limit 50 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
2/3 SYR4
Lead
1.215 µg/L 8.1%
of the EPA limit 15 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
Highest in the city: 1.433 µg/L — BIG BEND WATER SYSTEM · 80 people · 2019
3/3 SYR4
2,4-D
1 µg/L 1.4%
of the EPA limit 70 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2017
1/3 SYR4
Mercury
0.5600 µg/L 28%
of the EPA limit 2 µg/L
Highest in the city: CROW CREEK SIOUX TRIBE WATER SYSTEM · 130 people · 2019
2/3 SYR4
Chlordane
0.4400 µg/L 22%
of the EPA limit 2 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2017
1/3 SYR4
Atrazine
0.4300 µg/L 14%
of the EPA limit 3 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2018
1/3 SYR4
Antimony, Total
0.3945 µg/L 6.6%
of the EPA limit 6 µg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2019
1/3 SYR4
Lead
0.00066 mg/L 4.4%
of the EPA limit 0.0150 mg/L
Main supplier: FORT THOMPSON WATER SYSTEM · 1,357 people · 2025
Highest in the city: 0.0010 mg/L — CROW CREEK SIOUX TRIBE WATER SYSTEM · 130 people · 2025
3/3 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 Fort Thompson

SupplierPopulation served
FORT THOMPSON WATER SYSTEM 1,357
CROW CREEK SIOUX TRIBE WATER SYSTEM 130
BIG BEND WATER SYSTEM 80

Frequently asked questions about Fort Thompson tap water

Is Fort Thompson tap water safe to drink?

EPA testing detected 19 contaminants in the water serving Fort Thompson. 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 Fort Thompson?

3 public water suppliers report drinking-water monitoring for Fort Thompson, South Dakota to the EPA. Each is listed above with its population served.

What contaminants are in Fort Thompson's water?

The contaminants EPA monitoring detected in Fort Thompson include Fluoride, Copper, Nitrate, Nitrate-Nitrite, Nitrite. 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.