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Health problems are rare in tested Placer County wells.

All 7 health checks came back rare here.

From 52 wells tested in Placer County since 2000; your own well needs its own test. How to read this

Tested wells over the limit PlacerCalifornia
Arsenic5%2 of 41Nitrate2%1 of 52Manganese0%0 of 41Uranium0%0 of 41Radon0%0 of 10Fluoride0%0 of 45Lead0%0 of 23
GermsTest every year, whatever the chart says
Coliform bacteria24%6 of 25E. coli8%2 of 25
StainsNot a health risk
Iron stains7%3 of 41

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 5 people 79,205 people

Nobody else tests these wells. Only you do.

People on wells: EPA researchers' 2020 estimate

How deep wells go here

200 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)

Possible here. A home air test is inexpensive.

Radon zones: EPA map

Here's how Placer County compares with California and the counties around it.

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

All 7 health checks are rare in Placer County.

Arsenic2 of 41 wells over

2 of 41 wells tested here from 2005 to 2022 were over the EPA limit of 10 µg/L, against about 1 in 7 across California. Half the results were under 1.3 µg/L, and the top 1 in 10 were 4.6 µg/L or more. That's a smaller share than in 34 of the 46 other California counties with 10 or more tested wells.

Placer and its neighbors
Douglas, NV75%
Washoe, NV35%
Carson City, NV32%
Sutter26%
Sacramento18%
El Dorado7%
Nevada5%
Placer5%
Yuba0%

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

Arsenic guide

Nitrate1 of 52 wells over

1 of 52 wells tested here from 2000 to 2022 was over the EPA limit of 10 mg/L, against about 1 in 10 across California. Half the results were under 0.11 mg/L, and the top 1 in 10 were 2.3 mg/L or more. That's a smaller share than in 24 of the 46 other California counties with 10 or more tested wells.

Placer and its neighbors
Washoe, NV22%
Sutter5%
Douglas, NV4%
Carson City, NV2%
Placer2%
El Dorado2%
Nevada0%
Sacramento0%
Yuba0%

Nitrate guide

Manganese0 of 41 wells over

None of the 41 wells tested here from 2005 to 2022 were over the EPA health advisory of 0.3 mg/L, against about 1 in 12 across California. Half the results were under 0.00072 mg/L, and the top 1 in 10 were 0.04 mg/L or more. Placer County had none, while 42 of the 45 other California counties with 10 or more tested wells had at least one.

Placer and its neighbors
Sutter32%
El Dorado19%
Carson City, NV11%
Sacramento8%
Douglas, NV8%
Washoe, NV8%
Nevada5%
Yuba5%
Placer0%

Manganese guide

Uranium0 of 41 wells over

None of the 41 wells tested here from 2005 to 2022 were over the EPA limit of 30 µg/L, against about 1 in 13 across California. Half the results were under 0.26 µg/L, and the top 1 in 10 were 1.1 µg/L or more. Placer County had none, while 22 of the 43 other California counties with 10 or more tested wells had at least one.

Placer and its neighbors
Carson City, NV35%
Washoe, NV7%
El Dorado3%
Sacramento1%
Douglas, NV0%
Nevada0%
Placer0%
Sutter0%
Yuba0%

Uranium guide

Radon in water0 of 10 wells over

None of the 10 wells tested here from 2005 to 2008 were over 4,000 pCi/L, a level the EPA proposed, against about 1 in 30 across California. Half the results were under 530 pCi/L, and the top 1 in 10 were 1,590 pCi/L or more. Placer County had none, while 9 of the 28 other California counties with 10 or more tested wells had at least one, leaving out 1 county whose results are likely overstated.

Placer and its neighbors
El Dorado33%
Nevada0%
Placer0%
Sacramento0%
Washoe, NV0%

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

Too few tested to show: Carson City, NV, Douglas, NV, Sutter, Yuba.

Radon guide

Fluoride0 of 45 wells over

None of the 45 wells tested here from 2005 to 2022 were over the EPA limit of 4 mg/L, against about 1 in 37 across California. Half the results were under 0.18 mg/L, and the top 1 in 10 were 0.34 mg/L or more. Placer County had none, while 11 of the 44 other California counties with 10 or more tested wells had at least one.

Placer and its neighbors
Douglas, NV4%
Carson City, NV3%
El Dorado0%
Nevada0%
Placer0%
Sacramento0%
Sutter0%
Washoe, NV0%
Yuba0%
Lead0 of 23 wells over

None of the 23 wells tested here from 2005 to 2022 were over the EPA action level of 15 µg/L, against under 1 in 100 across California. Placer County had none, while 5 of the 42 other California counties with 10 or more tested wells had at least one.

Placer and its neighbors
Carson City, NV0%
Douglas, NV0%
El Dorado0%
Nevada0%
Placer0%
Sacramento0%
Sutter0%
Washoe, NV0%

Too few tested to show: Yuba.

Lead guide

Coliform bacteria turned up in 6 of 25 tested Placer County wells, so test for it every year.

Coliform bacteria6 of 25 wells had it

About 1 in 4 wells tested here from 2005 to 2017 had coliform bacteria, against about 2 in 10 across California.

Placer and its neighbors
El Dorado32%
Placer24%
Nevada18%
Sutter15%
Yuba11%
Sacramento9%
Carson City, NV8%
Washoe, NV4%

Too few tested to show: Douglas, NV.

Bacteria guide

E. coli2 of 25 wells had it

2 of 25 wells tested here from 2005 to 2017 had E. coli, against about 1 in 23 across California.

Placer and its neighbors
Placer8%
Nevada8%
El Dorado6%
Carson City, NV0%
Sacramento0%
Sutter0%
Washoe, NV0%
Yuba0%

Too few tested to show: Douglas, NV.

E. coli means human or animal waste is getting in, so if a test of your Placer County well finds it, boil drinking water until the well is fixed.

Bacteria guide

Iron reached staining levels in 3 of 41 tested wells, and it isn't a health risk.

Iron stains3 of 41 wells had it

3 of 41 wells tested here from 2005 to 2022 had enough iron to stain (0.3 mg/L), against about 1 in 10 across California.

Placer and its neighbors
El Dorado28%
Sutter16%
Nevada10%
Sacramento8%
Placer7%
Douglas, NV6%
Yuba5%
Washoe, NV4%
Carson City, NV0%

Iron guide

Placer County has 52 tested wells, and the busiest decade for testing was the 2010s.

23 wells had a test in the 2000s, 33 in the 2010s and 10 since 2020.

Only 10 of the 52 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.

Most Placer 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 3 things to check in Placer County.

  • Bacteria
  • Nitrate
  • Arsenic

What California offers well owners

Half the household wells here are shallower than 200 feet.

That comes from 15,248 household wells in California's drilling records. Most wells of every kind here are 125 to 320 feet deep. Wells as deep as Placer 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 are shallower than in 27 of the 56 other California counties with enough drilling records.

Look up your own well's depth in California'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 Placer County.

Placer County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide

Between 2023 and 2025 the EPA had 12 town water systems in Placer County test for PFAS. 1 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 4.3 ng/L of PFOS. Only 10 wells in Placer County have 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 Placer County
El DoradoNevadaSacramentoWashoe, NVDouglas, NV
Elsewhere in California
RiversideFresnoLos Angeles

All of California

Get a yearly reminder to test your Placer County well

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Questions people ask about well water in Placer County

Is well water in Placer County safe to drink?

Most tested wells in Placer County came in under the limits. Of 7 health checks with enough tests, arsenic came closest, at 2 of 41 wells over. Every well is different, so test yours for bacteria, nitrate and arsenic.

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

The State and Regional Water Boards fund or regulate 11 domestic well programs that offer free well testing in their service areas. If not, use a lab California has certified for drinking water. Ask for bacteria, nitrate and arsenic, the tests that matter most in Placer County.

How deep are wells in Placer County?

Half the household wells here are shallower than 200 feet. Typical household wells here are shallower than in 27 of the 56 other California counties with enough drilling records.

How does Placer County compare with the counties around it?

For arsenic, the share of tested wells over the limit: 7 of the 8 neighboring counties with data had a higher share than Placer County, at 5%. Douglas, NV had the most, at 75%. Groundwater doesn't stop at county lines, so Douglas, NV's 75% is worth knowing about if you live near it.

How often should I test my well in Placer County?

In Placer County, 6 of 25 tested wells had coliform bacteria, so the CDC's advice matters here: 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 State Water Resources Control BoardUpdated November 8, 2026

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Where the Placer County numbers come from

  • People on wells: 79,205 in Placer County, from EPA estimates built on the 2020 Census (Murray et al.).
  • Lab tests: 481 well water samples from 52 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2022.
  • Well depths: 15,248 California drilling records for Placer County, gathered in the US Groundwater Well Database (Lin and others, 2024).
  • Neighboring counties: the 8 counties that share a border with Placer County, from the Census Bureau's county adjacency file.
  • PFAS: EPA tests of 12 town water systems in Placer County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
  • Radon: Placer County is zone 2 on the EPA Map of Radon Zones.
  • State programs and links: State Water Resources Control Board, checked November 1, 2026.
Download this county's data (CSV)How we read these numbersReport an error
Test for bacteria and nitrate every yearSee lab tests