Well water in San Juan County, Utah
1in4
Testing strongly recommended
tested well samples in San Juan County exceeded the EPA limit for uranium (30 ug/L), based on public data from USGS Water Quality Portal.
3,416 test results across 13 contaminants from at least 292 wells, 1933 to 2022; chloride has the most at 631. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 9,783 people in San Juan 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 3% of the 9,783 people on private wells in San Juan County draw water above 10 ug/L (the model's range is 2% to 4%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside San Juan 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 |
|---|---|---|---|---|---|---|
| Uranium 1968 to 2022 | 130 | 95% | 6.89 | 16,300 | 30 ug/L EPA limit | |
| Arsenic 1968 to 2022 | 270 | 65% | 0.94 | 86 | 10 ug/L EPA limit | |
| Nitrate 1933 to 2022 | 261 | 67% | 0.1 | 99.6 | 10 mg/L EPA limit | |
| Lead 1977 to 2022 | 192 | 41% | 0 | 1,570 | 15 ug/L EPA limit | |
| Fluoride 1933 to 2022 | 357 | 94% | 0.5 | 14 | 4 mg/L EPA limit | |
| Copper 1955 to 2022 | 253 | 51% | 0 | 0.88 | 1.3 mg/L EPA limit | |
| Radium (226 + 228) 1983 to 2017 | 15 | 80% | 0.31 | 3.34 | 5 pCi/L EPA limit | |
| Chloride 1933 to 2022 | no limit | 631 | 100% | 37.5 | 464,000 | 250 mg/L nuisance level |
| Sodium 1949 to 2022 | no limit | 512 | 100% | 180 | 42,300 | 20 mg/L health guideline |
| Iron 1950 to 2022 | no limit | 444 | 81% | 90 | 224,000 | 300 ug/L nuisance level |
| Manganese 1950 to 2022 | no limit | 343 | 89% | 27 | 13,300 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: E. coli (4), Radon (4).
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Fluoride | 2%231 samples | 0%57 samples | 0%52 samples | 18%17 samples |
| Arsenic | 38%86 samples | 13%112 samples | 13%54 samples | 17%18 samples |
| Nitrate | 6%187 samples | 0%32 samples | 0%36 samples | n/a |
| Copper | 0%111 samples | 0%102 samples | 0%28 samples | 0%12 samples |
| Lead | 4%45 samples | 2%103 samples | 0%28 samples | 0%16 samples |
| Uranium | 81%32 samples | 7%45 samples | 9%35 samples | 22%18 samples |
Fluoride, arsenic, nitrate, copper, lead, uranium have held within a few points between the two most recent periods with enough samples.
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 uranium (28% of 130 samples), arsenic (21% of 270 samples), and nitrate (4% of 261 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, Iron, and Manganese 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 San Juan County
- 1Uranium28% of 130 local samples were above the limit.
- 2Arsenic21% of 270 local samples were above the limit.
- 3Nitrate4% of 261 local samples were above the limit.
- 4Lead2% of 192 local samples were above the limit.
- 5Fluoride2% of 357 local samples were above the limit.
- 6Coliform bacteriaRecommended for every private well, every year.
- 7RadonMedian local reading is 235 pCi/L.
- 8Volatile organic compounds (VOCs)55 leaking underground storage tank sites on record locally.
- 9Metals panel20 hazardous waste sites on record locally.
Test your San Juan County well for uranium, arsenic and nitrate
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 Utah: certified labs, state programs and prices.
Already have results back? Get your lab report read against the San Juan County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under San Juan County
Colorado Plateaus aquifers
Sandstone. Sandstone wells draw from pore space in the rock and tend to be dependable. Iron, manganese and hardness are common, and some sandstones carry arsenic or radium, so a first test should include both.
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 Utah
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.
- Drinking Water Consumer Information, Utah DEQ
- Certifications, Utah Public Health Laboratory
Contamination sources on record in San Juan County
Utah DEQ records 55 leaking underground storage tank sites and 20 hazardous waste sites in San Juan County, among 121 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.
- 55
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 20
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 46
- registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
Treatment that fits the local profile
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Lead
Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
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 uranium
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For uranium
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 lead
Aquasana Claryum 3-Stage under-sink filter
under-sink or countertop, about $175
Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.
For lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
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Common questions
Is there arsenic in well water in San Juan County?
Arsenic was detected in 65% of 270 public well samples in San Juan County, and 21% 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 often should I test a private well in San Juan 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 San Juan 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 Utah dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 3,416 samples in San Juan 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 9,783 people on private wells in San Juan 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.
- Utah DEQ regulated sites: 121 regulated sites located in San Juan County. Underground storage tank facilities, CERCLA site assessments and National Priorities List sites from the Utah 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.