Is Yellowtail Dam Gc Tap Water Safe? Quality Report

Water source: Ground water
Ownership: Federal government
Counties served: Big Horn

Compliance record

Formal violations the EPA has on file for this supplier. A health-based violation means a contaminant limit or a required treatment was breached; the rest are monitoring or reporting failures — still violations, but not a measured health risk.

health-based violations

226

violations on file

still open

Violation	Type	Status	Period
MR	Monitoring	Resolved	2024-12-30
MR	Monitoring	Resolved	2024-12-30
Other	Monitoring	Resolved	2023-07-01
Other	Monitoring	Resolved	2023-07-01
MR	Monitoring	Resolved	2017-01-01 → 2017-12-31
MR	Monitoring	Resolved	2017-01-01 → 2017-12-31
MR	Monitoring	Resolved	2017-01-01 → 2017-12-31
MR	Monitoring	Resolved	2017-01-01 → 2017-12-31
MR	Monitoring	Resolved	2015-12-30
MR	Monitoring	Resolved	2015-12-30

Other contaminants detected

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 this system's samples — over 100% is worth reading, but is not by itself a violation. Where a single sample came in higher than that percentile, it is noted under the bar. Formal violations are listed separately.

Contaminant	Level vs EPA limit	Detection rate	Source	Period
Copper	209 µg/L 16% of the EPA limit 1300 µg/L worst single sample: 230 µg/L	15/15	SYR4	2012–2018
Lead	0.0110 mg/L 73% of the EPA limit 0.0150 mg/L	12/12	LCR	2024
Nitrate-Nitrite	380 µg/L 3.8% of the EPA limit 10000 µg/L	12/12	SYR4	2012–2019
Lead	10.5 µg/L 70% of the EPA limit 15 µg/L worst single sample: 12 µg/L	11/15	SYR4	2012–2018
Bromodichloromethane	2.775 µg/L No EPA limit set worst single sample: 2.9 µg/L	6/6	SYR4	2012–2019
Chloroform	4.375 µg/L No EPA limit set worst single sample: 4.7 µg/L	6/6	SYR4	2012–2019
TTHM	8.325 µg/L 10% of the EPA limit 80 µg/L worst single sample: 8.8 µg/L	6/6	SYR4	2012–2019
Dibromochloromethane	1.1 µg/L No EPA limit set	5/6	SYR4	2012–2019
Arsenic	1 µg/L 10% of the EPA limit 10 µg/L	3/3	SYR4	2012–2019
Barium	169 µg/L 8.5% of the EPA limit 2000 µg/L worst single sample: 170 µg/L	3/3	SYR4	2012–2019
Dibromoacetic Acid	0.5690 µg/L No EPA limit set worst single sample: 0.6000 µg/L	3/3	SYR4	2013–2019
Fluoride	400 µg/L 10% of the EPA limit 4000 µg/L	3/3	SYR4	2012–2019
Total Haloacetic Acids (HAA5)	2.82 µg/L 4.7% of the EPA limit 60 µg/L worst single sample: 3 µg/L	3/3	SYR4	2013–2019
Dichloroacetic Acid	1.757 µg/L No EPA limit set worst single sample: 1.8 µg/L	2/3	SYR4	2013–2019
Trichloroacetic Acid	0.6100 µg/L No EPA limit set	1/3	SYR4	2013–2019

54 contaminants tested, none detected

1,1,1-Trichloroethane1,1,2-Trichloroethane1,1-Dichloroethylene1,2,4-Trichlorobenzene1,2-Dichloroethane1,2-Dichloropropane2,4,5-TP2,4-DAntimony, TotalAtrazineBhc-GammaBenzeneBenzo(A)PyreneBeryllium, TotalBromoformChlorobenzeneCadmiumCarbofuranCarbon TetrachlorideChlordaneChromiumDichloromethaneDalaponDi(2-ethylhexyl) AdipateDi(2-ethylhexyl) PhthalateDinosebEndrinEthylbenzeneHexachlorobenzeneHeptachlorHeptachlor EpoxideHexachlorocyclopentadieneLassoMercuryMethoxychlorMonobromoacetic AcidMonochloroacetic AcidOxamylPentachlorophenolPicloramSeleniumSimazineStyreneTetrachloroethyleneThallium, TotalTolueneToxapheneTrichloroethyleneVinyl ChlorideXylenes, Totalcis-1,2-DichloroethyleneO-DichlorobenzeneP-Dichlorobenzenetrans-1,2-Dichloroethylene

Utility contact

Contact: CURTIS, CHRIS
Phone: 406-666-3201
Email: [email protected]

Frequently asked questions about Yellowtail Dam Gc

Is Yellowtail Dam Gc tap water safe to drink?

EPA monitoring detected 15 contaminants in Yellowtail Dam Gc's water. A detection isn't the same as a violation — most levels are within federal limits. See each level and source above, and the utility's annual Consumer Confidence Report for its official compliance status.

What contaminants were detected in Yellowtail Dam Gc's water?

EPA monitoring detected Copper, Lead, Nitrate-Nitrite, Lead, Bromodichloromethane, and others. The full list with the level and data source for each is above.

How many people does Yellowtail Dam Gc serve?

Yellowtail Dam Gc reports serving 125 people in Montana, per its EPA record.

Has Yellowtail Dam Gc had any water quality violations?

The EPA has 226 violations on file for Yellowtail Dam Gc, of which 0 are health-based (a contaminant limit or required treatment was breached) and 0 remain open. The rest are monitoring or reporting failures.

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.