Tested Water
Menu

Uranium is widespread in Weld County wells.

1 widespread, 1 likely overstated, 1 worth checking, 3 rare out of 6 health checks.

From 22 wells tested in Weld County since 2002; your own well needs its own test. How to read this

Tested wells over the limit WeldColoradoLikely overstated
Nitrate71%15 of 21Uranium32%7 of 22Manganese14%3 of 22Arsenic0%0 of 22Lead0%0 of 22Fluoride0%0 of 22

Nitrate: All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it.

StainsNot a health risk
Iron stains0%0 of 22

Not charted, because fewer than 10 wells were tested: radon (1).

Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+

Lab results: Water Quality Portal (USGS and EPA)

Who drinks from a well here

1 in 10 people 31,749 people

Nobody else tests these wells. Only you do.

People on wells: EPA researchers' 2020 estimate

How deep wells go here

210 ft Near the surface: fertilizer, germs Deeper: arsenic, uranium from rock 500 ft

Deep wells: fewer surface germs, more minerals from the rock.

Well depths: US Groundwater Well Database

Radon risk (a gas from rock)

Likely here. Test your home's air first.

Radon zones: EPA map

Here's how Weld County compares with Colorado and the counties around it.

Each result puts Weld County next to the 8 counties that border it, on the chart's 0 to 50% scale.

This one is widespread in Weld County wells.

Uranium7 of 22 wells over

About 3 in 10 wells tested here from 2002 to 2023 were over the EPA limit of 30 µg/L, against about 2 in 10 across Colorado. Half the results were under 21 µg/L, and the top 1 in 10 were 40 µg/L or more. That's a bigger share than in 10 of the 12 other Colorado counties with 10 or more tested wells.

Weld and its neighbors
Weld32%
Adams22%
Laramie, WY0%

Too few tested to show: Boulder, Broomfield, Kimball, NE, Larimer, Logan, Morgan.

Uranium guide

This one has turned up often here, mostly from one small area.

Nitrate15 of 21 wells over

About 7 in 10 wells tested here from 2002 to 2023 were over the EPA limit of 10 mg/L, against about 1 in 10 across Colorado. Half the results were under 16 mg/L, and the top 1 in 10 were 37 mg/L or more. We don't rank this against other Colorado counties, because most of these tests come from one small area.

Weld and its neighbors
Weld71%
Adams25%
Laramie, WY2%

* Likely overstated, so we don't rank it.

Too few tested to show: Boulder, Broomfield, Kimball, NE, Larimer, Logan, Morgan.

All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it.

Nitrate guide

This one is worth checking in Weld County.

Manganese3 of 22 wells over

3 of 22 wells tested here from 2002 to 2023 were over the EPA health advisory of 0.3 mg/L, against about 2 in 10 across Colorado. At least half the results were too low for the lab to measure, and the top 1 in 10 were 0.27 mg/L or more. That's a bigger share than in 12 of the 19 other Colorado counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated.

Weld and its neighbors
Adams14%
Weld14%
Laramie, WY0%

Too few tested to show: Boulder, Broomfield, Kimball, NE, Larimer, Logan, Morgan.

Manganese guide

These 3 are rare in Weld County.

Arsenic0 of 22 wells over

None of the 22 wells tested here from 2002 to 2023 were over the EPA limit of 10 µg/L, against about 1 in 8 across Colorado. Half the results were under 0.95 µg/L, and the top 1 in 10 were 3.8 µg/L or more. Weld County had none, while 8 of the 11 other Colorado counties with 10 or more tested wells had at least one, leaving out 2 counties whose results are likely overstated.

Weld and its neighbors
Laramie, WY6%
Adams3%
Weld0%

Too few tested to show: Boulder, Broomfield, Kimball, NE, Larimer, Logan, Morgan.

Arsenic guide

Lead0 of 22 wells over

None of the 22 wells tested here from 2002 to 2023 were over the EPA action level of 15 µg/L, against about 1 in 26 across Colorado. At least half the results were too low for the lab to measure, and the top 1 in 10 were 0.21 µg/L or more. Weld County had none, while 3 of the 12 other Colorado counties with 10 or more tested wells had at least one.

Weld and its neighbors
Adams0%
Laramie, WY0%
Weld0%

Too few tested to show: Boulder, Broomfield, Kimball, NE, Larimer, Logan, Morgan.

Lead guide

Fluoride0 of 22 wells over

None of the 22 wells tested here from 2002 to 2023 were over the EPA limit of 4 mg/L, against about 1 in 26 across Colorado. Half the results were under 1.1 mg/L, and the top 1 in 10 were 1.6 mg/L or more. Weld County had none, while 4 of the 16 other Colorado counties with 10 or more tested wells had at least one, leaving out 3 counties whose results are likely overstated.

Weld and its neighbors
Adams0%
Laramie, WY0%
Weld0%

Too few tested to show: Boulder, Broomfield, Kimball, NE, Larimer, Logan, Morgan.

Too few Weld County wells were tested for this one.

Radon in water1 well tested

Only 1 well here was tested in 2005, too few to say how common it is. Across Colorado it's about 1 in 8.

Radon guide

Every well needs a bacteria test every year.

No bacteria tests from Weld County wells are in the public data. Test every year anyway.

Iron reached staining levels in 0 of 22 tested wells, and it isn't a health risk.

Iron stains0 of 22 wells had it

None of the 22 wells tested here from 2002 to 2023 had enough iron to stain, against about 2 in 10 across Colorado.

Weld and its neighbors
Laramie, WY3%
Adams3%
Weld0%

Too few tested to show: Boulder, Broomfield, Kimball, NE, Larimer, Logan, Morgan.

Iron guide

Most of the 22 wells tested in Weld County were last tested before 2010.

21 wells had a test in the 2000s, 4 in the 2010s and 5 since 2020.

An old result shows the water as it was then, so treat these 22 wells as a starting point and test your own.

Most Weld County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).

One mail-in lab test covers the 5 things to check in Weld County.

  • Bacteria
  • Nitrate
  • Uranium
  • Manganese
  • Arsenic

What Colorado offers well owners

Half the household wells here are shallower than 210 feet.

That comes from 10,729 household wells in Colorado's drilling records. Most wells of every kind here are 48 to 350 feet deep. Wells as deep as Weld County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium. Typical household wells here go deeper than in 44 of the 63 other Colorado counties with enough drilling records.

Look up your own well's depth in Colorado's well record search, or see how to find it.

Well depths: US Groundwater Well Database

Here's what we know about radon and PFAS in Weld County.

Weld County is in the EPA's highest radon zone. Radon from well water adds to the radon in your indoor air, so test your air first, and your water too if the air is high. Radon guide

Between 2023 and 2025 the EPA had 15 town water systems in Weld County test for PFAS. 1 found some PFAS, all below the new limits. No well in Weld County has public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide

Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025

Next door to Weld County
Laramie, WY
Elsewhere in Colorado
El PasoDouglasLa PlataElbert

All of Colorado

Get a yearly reminder to test your Weld County well

We'll email you a copy of this page now and one reminder a year. Nothing else. Privacy

Questions people ask about well water in Weld County

Is well water in Weld County safe to drink?

15 of 21 wells tested in Weld County had nitrate over the limit, about 7 in 10. Across Colorado it's about 1 in 10. We don't rank this against other Colorado counties, because most of these tests come from one small area. All of these tests come from the US Geological Survey in one small part of the county, so this likely overstates it. So test your own well for nitrate before you count on it.

Can I get my well tested for free in Weld County?

CDPHE offers free PFAS testing for private wells through its PFAS Testing and Assistance Program. If not, use a lab Colorado has certified for drinking water. Ask for bacteria, nitrate, uranium, manganese and arsenic, the tests that matter most in Weld County.

How deep are wells in Weld County?

Half the household wells here are shallower than 210 feet. Typical household wells here go deeper than in 44 of the 63 other Colorado counties with enough drilling records.

How does Weld County compare with the counties around it?

For nitrate, the share of tested wells over the limit: Weld County, at 71%, had a higher share than all 2 neighboring counties with data. Groundwater doesn't stop at county lines, so Adams's 25% is worth knowing about if you live near it.

How often should I test my well in Weld County?

Weld County has no public bacteria results for wells, so follow the CDC's advice: test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.

By the Tested Water teamData from the USGS, EPA and Department of Public Health and EnvironmentUpdated November 8, 2026

If you buy something through our links, we may earn a commission. We'd recommend the same thing either way, and we'll tell you when a free option exists. How we make money

Where the Weld County numbers come from

  • People on wells: 31,749 in Weld County, from EPA estimates built on the 2020 Census (Murray et al.).
  • Lab tests: 241 well water samples from 22 wells in the Water Quality Portal, run by the USGS and EPA, 2002 to 2023.
  • Well depths: 10,729 Colorado drilling records for Weld County, gathered in the US Groundwater Well Database (Lin and others, 2024).
  • Neighboring counties: the 8 counties that share a border with Weld County, from the Census Bureau's county adjacency file.
  • Results marked likely overstated: our own check of who tested the wells, when and where.
  • PFAS: EPA tests of 15 town water systems in Weld County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
  • Radon: Weld County is zone 1 on the EPA Map of Radon Zones.
  • State programs and links: Department of Public Health and Environment, checked November 1, 2026.
Download this county's data (CSV)How we read these numbersReport an error
One lab test covers what to check in Weld CountyFind a lab test