Arsenic in Montana well water

In Montana, 10% of 5,666 tested private well samples exceeded the EPA limit for arsenic (10 ug/L).

Arsenic occurs naturally in New England bedrock and dissolves into well water. Long-term exposure raises the risk of bladder, lung and skin cancers, and is linked to heart disease and lower IQ in children. It has no taste or smell, so testing is the only way to know.

Check your arsenic number

Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.

Test your Montana well for arsenic

Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.

Order the Tap Score well water test kit, from $209 Already tested? Upload the report

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Systems that remove arsenic

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For arsenic

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For arsenic

Whole-house arsenic and uranium filter

whole-house, at the point of entry, about $2,500

Adsorptive iron-based media; sized to your well yield.

For arsenic

Aquasana SmartFlow reverse osmosis

under-sink or countertop, about $225

Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.

Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.

Where to get a well tested for arsenic in Montana: certified labs, state programs and prices.

By county, from individual samples

Public monitoring samples against the EPA limit (10 ug/L); counties with at least 30 samples.

County	Above EPA limit	Samples	Detected	Median	Highest
Gallatin	52%	229	84%	12.8	176 ug/L
Roosevelt	46%	54	100%	9.9	316 ug/L
Powell	28%	246	56%	4.5	158 ug/L
Madison	23%	30	70%	2	140 ug/L
Silver Bow	23%	473	89%	6	117 ug/L
Jefferson	22%	220	94%	0.595	19,200 ug/L
Deer Lodge	17%	125	90%	2	115 ug/L
Sheridan	16%	37	49%	0	33 ug/L
Beaverhead	14%	42	98%	2.85	28 ug/L
Phillips	13%	32	81%	2	17.5 ug/L
Valley	11%	66	70%	1.2	37.3 ug/L
McCone	11%	38	68%	0.1	24 ug/L
Richland	9%	56	79%	0.65	506 ug/L
Lewis and Clark	9%	366	71%	0.61	49.9 ug/L
Cascade	7%	54	78%	0.6	530 ug/L

Three Forks CCD, Gallatin County78% of 119
Manhattan CCD, Gallatin County67% of 30
Fort Peck Reservation CCD, Roosevelt County47% of 53
Anaconda CCD, Deer Lodge County46% of 39
Deer Lodge CCD, Powell County29% of 231
Butte-Silver Bow Northwest CCD, Silver Bow County27% of 229
Boulder CCD, Jefferson County22% of 220
Butte CCD, Silver Bow County19% of 244
West Yellowstone CCD, Gallatin County14% of 35
Dillon CCD, Beaverhead County10% of 39
Helena CCD, Lewis and Clark County9% of 339
Hamilton CCD, Ravalli County8% of 39
Otter CCD, Powder River County6% of 775
Blackfeet Reservation CCD, Glacier County6% of 49
Ashland CCD, Rosebud County4% of 56
Warm Springs CCD, Deer Lodge County3% of 86
Decker CCD, Big Horn County3% of 94
Rosebud CCD, Rosebud County1% of 2,017
Stevensville CCD, Ravalli County0% of 32
Kalispell CCD, Flathead County0% of 46

Sources

Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. arsenic counts and shares are listed on each county and town page with their sources.

Analysis: Arsenic in private wells, state by state, from the same public records.