Well water in El Dorado County, California
In El Dorado County, 4% of 591 tested well samples exceeded the EPA limit for arsenic (10 ug/L), based on public data from California GAMA Domestic Well Project and USGS Water Quality Portal.
The strongest signal is PFOA: 8% of 13 local samples were above the limit, too few samples to carry the headline but first on the test list below.
6,835 test results across 16 contaminants from at least 535 wells, 1986 to 2023; nitrate has the most at 1,314. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 28,188 people in El Dorado County get their drinking water from a private well, per USGS 2015 county water use. That is about 15% of residents.
Separately, the USGS national arsenic model estimates that <1% of the 28,188 people on private wells in El Dorado County draw water above 10 ug/L, from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside El Dorado 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 |
|---|---|---|---|---|---|---|
| PFOA 2021 to 2023 | 13 | 23% | 0 | 5 | 4 ng/L EPA limit | |
| Arsenic 1990 to 2023 | 591 | 38% | 0 | 142 | 10 ug/L EPA limit | |
| Uranium 1986 to 2023 | 207 | 91% | 1.9 | 60 | 30 ug/L EPA limit | |
| Nitrate 1986 to 2023 | 1,314 | 83% | 0.084 | 47.4 | 10 mg/L EPA limit | |
| Lead 1989 to 2023 | 601 | 14% | 0 | 110 | 15 ug/L EPA limit | |
| Fluoride 1986 to 2023 | 712 | 46% | 0 | 1.6 | 4 mg/L EPA limit | |
| Copper 1989 to 2023 | 601 | 25% | 0 | 0.44 | 1.3 mg/L EPA limit | |
| Radium (226 + 228) 2007 to 2008 | 16 | 50% | 0.009 | 3.04 | 5 pCi/L EPA limit | |
| Gross alpha 2003 | 15 | 100% | 0.58 | 7.64 | 15 pCi/L EPA limit | |
| PFOS 2021 to 2023 | 13 | 23% | 0 | 2.5 | 4 ng/L EPA limit | |
| Iron 1986 to 2023 | no limit | 848 | 57% | 30 | 87,000 | 300 ug/L nuisance level |
| Chloride 1986 to 2023 | no limit | 719 | 100% | 9.2 | 425 | 250 mg/L nuisance level |
| Manganese 1986 to 2023 | no limit | 711 | 52% | 0.96 | 1,800 | 300 ug/L health guideline |
| Sodium 2002 to 2004 | no limit | 400 | 100% | 9.8 | 330 | 20 mg/L health guideline |
| Radon 1989 to 2008 | no limit | 68 | 100% | 1,290 | 12,000 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: Nitrite (6).
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 |
|---|---|---|---|---|
| Nitrate | <1%216 samples | <1%978 samples | 6%94 samples | 4%26 samples |
| Fluoride | 0%50 samples | 0%603 samples | 0%46 samples | 0%13 samples |
| Lead | 0%33 samples | <1%508 samples | 0%47 samples | 0%13 samples |
| Copper | 0%33 samples | 0%508 samples | 0%47 samples | 0%13 samples |
| Arsenic | 22%23 samples | 3%508 samples | 4%47 samples | 8%13 samples |
| Uranium | 5%39 samples | 2%108 samples | 0%47 samples | 0%13 samples |
Nitrate, fluoride, lead, copper, arsenic, 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 pfoa (8% of 13 samples), arsenic (4% of 591 samples), and uranium (2% of 207 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.
Iron, Chloride, 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 El Dorado County
- 1PFOA8% of 13 local samples were above the limit.
- 2Arsenic4% of 591 local samples were above the limit.
- 3Uranium2% of 207 local samples were above the limit.
- 4Nitrate1% of 1,314 local samples were above the limit.
- 5Lead<1% of 601 local samples were above the limit.
- 6Coliform bacteriaRecommended for every private well, every year.
- 7RadonMedian local reading is 1,290 pCi/L.
- 8Volatile organic compounds (VOCs)209 leaking underground storage tank sites on record locally.
Test your El Dorado County well for PFOA, arsenic and uranium
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 California: certified labs, state programs and prices.
Already have results back? Get your lab report read against the El Dorado County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under El Dorado County
Not a principal aquifer
The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.
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 California
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.
- GAMA - Well Owners, State Water Resources Control Board
- Environmental Laboratory Accreditation Program (ELAP), State Water Resources Control Board
Contamination sources on record in El Dorado County
California GeoTracker and EnviroStor sites records 209 leaking underground storage tank sites in El Dorado County, among 296 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.
- 209
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 5
- lined landfills and transfer facilities
- 82
- other remediation projects
Treatment that fits the local profile
PFOA
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Uranium
Point-of-use reverse osmosis; Anion exchange; 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
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 PFOA
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For PFOA
Whole-house PFAS carbon system
whole-house, at the point of entry, about $3,000
Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.
For PFOA
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 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 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 El Dorado County?
Arsenic was detected in 38% of 591 public well samples in El Dorado County, and 4% 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 El Dorado County?
The median radon level across 68 public samples in El Dorado County was 1,290 pCi/L, with a high of 12,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in El Dorado 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 El Dorado 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 California dataset as CSV, every county and town, with the sources named.
Sources
- California GAMA Domestic Well Project: 3,620 samples in El Dorado County. Private well samples from the State Water Board GAMA Domestic Well Project county studies (El Dorado, Tehama, Tulare, San Diego, Yuba, Monterey and others), 2002 to 2011, from the GAMA results file on data.ca.gov. Retrieved September 15, 2026.
- USGS Water Quality Portal: 3,215 samples in El Dorado 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 28,188 people on private wells in El Dorado 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.
- California GeoTracker and EnviroStor sites: 296 regulated sites located in El Dorado County. Leaking underground storage tank and cleanup sites from the State Water Board GeoTracker export on data.ca.gov, and DTSC EnviroStor cleanup sites. Retrieved September 15, 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.