Well water in Columbia County, Washington
No public well test results have been compiled for Columbia County yet. The USGS national arsenic model estimates that 2% of the 1,074 people on private wells there draw water with arsenic above 10 ug/L, the EPA limit, based on geology, well depth and land use rather than local tests.
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.
91 test results across 9 contaminants from at least 11 wells, 1959 to 1983; nitrate has the most at 15. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 1,074 people in Columbia County get their drinking water from a private well, per USGS 2015 county water use. That is about 27% of residents.
Separately, the USGS national arsenic model estimates that 2% of the 1,074 people on private wells in Columbia 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 Columbia 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 |
|---|---|---|---|---|---|---|
| Nitrate 1959 to 1983 | 15 | 100% | 1 | 10 | 10 mg/L EPA limit | |
| Fluoride 1959 to 1983 | 15 | 100% | 0.3 | 0.5 | 4 mg/L EPA limit | |
| Iron 1959 to 1983 | no limit | 15 | 53% | 0 | 430 | 300 ug/L nuisance level |
| Chloride 1959 to 1983 | no limit | 15 | 100% | 2.4 | 17 | 250 mg/L nuisance level |
| Sodium 1959 to 1983 | no limit | 15 | 100% | 8.8 | 18 | 20 mg/L health guideline |
| Manganese 1972 to 1983 | no limit | 11 | 45% | 0 | 0 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Copper (2), Lead (2), Arsenic (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 Columbia County came back above it. That is reassuring, but sampling is uneven: wells that were never tested are not in this data.
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 Columbia County
- 1Coliform bacteriaRecommended for every private well, every year.
- 2NitrateRecommended for every private well, especially near farms or septic systems.
- 3FluorideDetected in 100% of local samples.
- 4ChlorideDetected in 100% of local samples.
- 5IronDetected in 53% of local samples.
- 6Volatile organic compounds (VOCs)1 reported spill or release on record locally.
Test your Columbia County well for coliform bacteria, nitrate and fluoride
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 Washington: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Columbia County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Columbia County
315 domestic wells in Columbia County are on record with the state since 1993. the typical well is 275 feet deep (one in ten goes past 600 feet).
In a typical Columbia County well, the median yield is 45 gallons per minute.
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open Ecology well report search and choose Water Well.
- It lists depth, casing, static water level, the yield test and the driller.
Washington has required well reports since 1971; reports are located only to the quarter-quarter section, so check the address on the scan.
The rock under Columbia County
Columbia Plateau basin-fill aquifers
Unconsolidated sand and gravel. Wells in sand and gravel are usually shallow and productive, and they recharge quickly from the surface. That makes them the most exposed to nitrate, bacteria and anything spilled nearby, and the least likely to carry arsenic or radon from the rock.
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 Washington
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.
- Drinking Water, Washington State Department of Health
- Environmental lab accreditation, Washington State Department of Ecology
Contamination sources on record in Columbia County
Washington Ecology facility interactions records 1 reported spill or release in Columbia County, among 64 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
- reported spill or releaseMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 56
- other remediation projects
- 7
- other solid waste facilities
Free, no obligation
Get on the list for a free in-home water test in Columbia County
No water treatment company serves Columbia 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 Columbia County, and you get an email naming it first.
Common questions
How deep are wells in Columbia County?
The typical domestic well in Columbia County is 275 feet deep, based on 315 wells reported to the state since 1993. One in ten is deeper than 600 feet.
How often should I test a private well in Columbia 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 Columbia 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 Washington dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 91 samples in Columbia 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 1,074 people on private wells in Columbia 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.
- Washington Ecology well construction reports: 315 well records in Columbia County, 315 domestic. Well construction reports filed with the Washington State Department of Ecology, water wells only, located at the quarter-quarter section. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 17, 2026.
- Washington Ecology facility interactions: 64 regulated sites located in Columbia County. Toxics cleanup sites, spills and solid waste facilities from the Washington State Department of Ecology Facility/Site register. Retrieved September 17, 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.