Well water in Lake County, Colorado
In Lake County, none of 35 tested well samples exceeded the EPA limit for fluoride, based on public data from USGS Water Quality Portal.
The strongest signal is coliform bacteria: Recommended for every private well, every year, too few samples to carry the headline but first on the test list below.
223 test results across 8 contaminants from at least 40 wells, 1972 to 2010; manganese has the most at 49. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 3,365 people in Lake County get their drinking water from a private well, per USGS 2015 county water use. That is about 45% of residents.
Separately, the USGS national arsenic model estimates that 2% of the 3,365 people on private wells in Lake 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 Lake 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 |
|---|---|---|---|---|---|---|
| Fluoride 1972 to 2008 | 35 | 89% | 0.2 | 2.9 | 4 mg/L EPA limit | |
| Copper 1972 to 2010 | 24 | 83% | 0.002 | 0.046 | 1.3 mg/L EPA limit | |
| Lead 1972 to 2010 | 24 | 88% | 0.25 | 3.19 | 15 ug/L EPA limit | |
| Arsenic 1972 to 2010 | 22 | 91% | 0.24 | 4.39 | 10 ug/L EPA limit | |
| Uranium 2006 to 2010 | 20 | 85% | 0.126 | 1.23 | 30 ug/L EPA limit | |
| Manganese 1972 to 2010 | no limit | 49 | 63% | 0 | 517 | 300 ug/L health guideline |
| Iron 1972 to 2010 | no limit | 48 | 90% | 40 | 4,420 | 300 ug/L nuisance level |
Sampled fewer than 10 times, too few to summarize: Chloride (1).
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
Among contaminants with a federal limit, no tested sample in Lake County came back above it. That is reassuring, but sampling is uneven: wells that were never tested are not in this data.
Manganese, Iron, 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 Lake County
- 1Coliform bacteriaRecommended for every private well, every year.
- 2NitrateRecommended for every private well, especially near farms or septic systems.
- 3ChlorideDetected in 100% of local samples.
- 4IronDetected in 90% of local samples.
- 5FluorideDetected in 89% of local samples.
- 6CopperDetected in 83% of local samples.
- 7ManganeseDetected in 63% of local samples.
Test your Lake County well for coliform bacteria, nitrate and chloride
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 Colorado: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Lake County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Lake 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 Colorado
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.
Contamination sources on record in Lake County
CDPHE operating landfills records 1 regulated sites in Lake County, among 1 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.
- 1
- lined landfill or transfer facility
Treatment that fits the local profile
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
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 iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Lake County
No water treatment company serves Lake 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 Lake County, and you get an email naming it first.
Common questions
Is there arsenic in well water in Lake County?
Arsenic was detected in 91% of 22 public well samples in Lake County, and 0% 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 Lake 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 Lake 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 Colorado dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 223 samples in Lake 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 3,365 people on private wells in Lake 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.
- CDPHE operating landfills: 1 regulated sites located in Lake County. Operating commercial landfills from the Colorado Department of Public Health and Environment. 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.