Well water in Nevada County, California

1in12

Testing recommended

tested well samples in Nevada County exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal and California GAMA Domestic Well Project.

559 test results across 14 contaminants from at least 68 wells, 1961 to 2022; nitrate has the most at 87. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

An estimated 29,355 people in Nevada County get their drinking water from a private well, per USGS 2015 county water use. That is about 30% of residents.

Separately, the USGS national arsenic model estimates that 2% of the 29,355 people on private wells in Nevada County draw water above 10 ug/L (the model's range is 2% to 3%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Nevada 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 2002 to 2022	8%	83	83%	0.41	34.7	10 ug/L EPA limit
PFOA 2020 to 2022	8%	12	8%	0	7.3	4 ng/L EPA limit
PFOS 2020 to 2022	8%	12	17%	0	4.9	4 ng/L EPA limit
Nitrate 1961 to 2022	3%	87	67%	0.204	18.8	10 mg/L EPA limit
Copper 2002 to 2022	0%	83	59%	0.001	0.21	1.3 mg/L EPA limit
Lead 2002 to 2022	0%	83	64%	0.1	4.4	15 ug/L EPA limit
Uranium 2007 to 2022	0%	80	69%	0.048	9.83	30 ug/L EPA limit
Manganese 1980 to 2022	no limit	85	58%	1.09	767	300 ug/L health guideline
Radon 2007 to 2008	no limit	16	100%	785	1,950	2,000 pCi/L health guideline

Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (6), Fluoride (3), Chloride (3), Iron (3), Sodium (3).

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
Arsenic	n/a	18%22 samples	4%49 samples	8%12 samples
Copper	n/a	0%22 samples	0%49 samples	0%12 samples
Lead	n/a	0%22 samples	0%49 samples	0%12 samples
Nitrate	n/a	0%20 samples	4%49 samples	8%12 samples
Uranium	n/a	0%19 samples	0%49 samples	0%12 samples

Arsenic above the limit in Nevada County fell from 18% of 22 samples in the 2000s to 4% of 49 in the 2010s.

Copper, lead, nitrate 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 address

What this means

The contaminants most often above their limit here are arsenic (8% of 83 samples), pfoa (8% of 12 samples), and pfos (8% of 12 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.

Manganese and Chloride 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 Nevada County

1
Arsenic
8% of 83 local samples were above the limit.
2
PFOA
8% of 12 local samples were above the limit.
3
PFOS
8% of 12 local samples were above the limit.
4
Nitrate
3% of 87 local samples were above the limit.
5
Coliform bacteria
Recommended for every private well, every year.
6
Radon
Median local reading is 785 pCi/L.
7
Chloride
Detected in 100% of local samples.
8
Volatile organic compounds (VOCs)
223 leaking underground storage tank sites on record locally.
9
Metals panel
7 hazardous waste sites on record locally.

Test your Nevada County well for arsenic, PFOA and PFOS

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 $209 Already 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 Nevada County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

The rock under Nevada 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 Nevada County

California GeoTracker and EnviroStor sites records 223 leaking underground storage tank sites and 7 hazardous waste sites in Nevada County, among 422 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.

223: leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
7: hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
26: lined landfills and transfer facilities
166: other remediation projects

Treatment that fits the local profile

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

PFOA

Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange

PFOS

Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

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 PFOA

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 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 HealthShield whole-house filter

whole-house, at the point of entry, about $2,099

Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.

Free, no obligation

Get on the list for a free in-home water test in Nevada County

No water treatment company serves Nevada 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 Nevada County, and you get an email naming it first.

Common questions

Is there arsenic in well water in Nevada County?

Arsenic was detected in 83% of 83 public well samples in Nevada County, and 8% 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 Nevada County?

The median radon level across 16 public samples in Nevada County was 785 pCi/L, with a high of 1,950 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Nevada 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 Nevada 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

USGS Water Quality Portal: 534 samples in Nevada 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.
California GAMA Domestic Well Project: 25 samples in Nevada 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 national arsenic model (Ayotte 2017): estimated share of 29,355 people on private wells in Nevada 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: 422 regulated sites located in Nevada 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.