Well water in Broadwater County, Montana
In Broadwater County, none of 77 tested well samples exceeded the EPA limit for fluoride, based on public data from USGS Water Quality Portal.
The strongest signal is arsenic: 14% of 28 local samples were above the limit, too few samples to carry the headline but first on the test list below.
489 test results across 11 contaminants from at least 82 wells, 1949 to 2010; chloride has the most at 89. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 3,539 people in Broadwater County get their drinking water from a private well, per USGS 2015 county water use. That is about 62% of residents.
Separately, the USGS national arsenic model estimates that 9% of the 3,539 people on private wells in Broadwater County draw water above 10 ug/L (the model's range is 7% to 13%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Broadwater County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Arsenic 1979 to 1993 | 28 | 93% | 2.35 | 35.4 | 10 ug/L EPA limit | |
| Nitrate 1977 to 2010 | 13 | 85% | 0.37 | 17.8 | 10 mg/L EPA limit | |
| Fluoride 1949 to 2010 | 77 | 97% | 0.5 | 1.8 | 4 mg/L EPA limit | |
| Copper 1983 to 1993 | 22 | 27% | 0 | 0.03 | 1.3 mg/L EPA limit | |
| Lead 1983 to 1993 | 22 | 0% | 0 | 0 | 15 ug/L EPA limit | |
| Chloride 1949 to 2010 | no limit | 89 | 100% | 17 | 136 | 250 mg/L nuisance level |
| Iron 1949 to 2010 | no limit | 87 | 77% | 30 | 55,000 | 300 ug/L nuisance level |
| Sodium 1949 to 2010 | no limit | 82 | 100% | 39.6 | 414 | 20 mg/L health guideline |
| Manganese 1977 to 2010 | no limit | 51 | 35% | 0 | 1,260 | 300 ug/L health guideline |
| Radon 1992 to 2010 | no limit | 12 | 100% | 760 | 3,800 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: Uranium (6).
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
The contaminants most often above their limit here are arsenic (14% of 28 samples) and nitrate (8% of 13 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride and Iron are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Broadwater County
- 1Arsenic14% of 28 local samples were above the limit.
- 2Nitrate8% of 13 local samples were above the limit.
- 3Coliform bacteriaRecommended for every private well, every year.
- 4RadonMedian local reading is 760 pCi/L.
- 5ChlorideDetected in 100% of local samples.
- 6FluorideDetected in 97% of local samples.
- 7IronDetected in 77% of local samples.
- 8Volatile organic compounds (VOCs)45 leaking underground storage tank sites on record locally.
Test your Broadwater County well for arsenic, nitrate and coliform bacteria
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 $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in Montana: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Broadwater County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Broadwater County
Northern Rocky Mountains Intermontane Basins aquifer system
Unconsolidated sand and gravel. Wells in sand and gravel are usually shallow and productive, and they recharge quickly from the surface. That makes them the most exposed to nitrate, bacteria and anything spilled nearby, and the least likely to carry arsenic or radon from the rock.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Montana
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Water Resources, Montana DEQ
- Water Laboratory Certification Program, Montana DPHHS
Contamination sources on record in Broadwater County
Montana DEQ records 45 leaking underground storage tank sites in Broadwater County, among 66 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 45
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 6
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
- 15
- other solid waste facilities
Treatment that fits the local profile
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
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.
For iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Broadwater County
No water treatment company serves Broadwater County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Broadwater County, and you get an email naming it first.
Common questions
Is there arsenic in well water in Broadwater County?
Arsenic was detected in 93% of 28 public well samples in Broadwater County, and 14% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Broadwater County?
The median radon level across 12 public samples in Broadwater County was 760 pCi/L, with a high of 3,800 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Broadwater County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Counties near Broadwater County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the Montana dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 489 samples in Broadwater County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 3,539 people on private wells in Broadwater County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- Montana DEQ regulated sites: 66 regulated sites located in Broadwater County. Petroleum tank releases, underground storage tank facilities and licensed solid waste facilities from the Montana Department of Environmental Quality. Retrieved September 18, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.