Health problems are rare in tested Shasta County wells.
All 7 health checks came back rare here.
From 60 wells tested in Shasta County since 2007; your own well needs its own test. How to read this
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 37,596 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Deep wells: fewer surface germs, more minerals from the rock.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Less likely, but the EPA still says test your air.
Radon zones: EPA map
Here's how Shasta County compares with California and the counties around it.
Each result puts Shasta County next to the 6 counties that border it, on the chart's 0 to 50% scale.
All 7 health checks are rare in Shasta County.
Manganese2 of 58 wells over
Too few tested to show: Plumas, Trinity.
Arsenic0 of 60 wells over
Too few tested to show: Plumas.
Nitrate0 of 60 wells over
Too few tested to show: Plumas.
Uranium0 of 60 wells over
Too few tested to show: Modoc, Plumas.
Radon in water0 of 25 wells over
Too few tested to show: Modoc, Plumas, Tehama.
Fluoride0 of 60 wells over
Too few tested to show: Modoc, Plumas.
Lead0 of 32 wells over
Too few tested to show: Lassen, Plumas, Trinity.
Coliform bacteria turned up in 5 of 37 tested Shasta County wells, so test for it every year.
Coliform bacteria5 of 37 wells had it
Too few tested to show: Modoc, Plumas.
E. coli1 of 37 wells had it
Too few tested to show: Modoc, Plumas.
E. coli means human or animal waste is getting in, so if a test of your Shasta County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 3 of 60 tested wells, and it isn't a health risk.
Iron stains3 of 60 wells had it
Too few tested to show: Plumas.
Shasta County has 60 tested wells, and the busiest decade for testing was the 2010s.
Only 7 of the 60 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Shasta 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 Shasta County.
- Bacteria
- Nitrate
- Arsenic
What California offers well owners
- Free testingThe State and Regional Water Boards fund or regulate 11 domestic well programs that offer free well testing in their service areas. See the program
- Certified labsCalifornia's list of certified labs
- Well recordsCalifornia's well record search
Half the household wells here are shallower than 160 feet.
That comes from 11,941 household wells in California's drilling records. Most wells of every kind here are 102 to 240 feet deep. Wells as deep as Shasta 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 42 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 Shasta County.
Shasta County is in the EPA's lowest radon zone, so radon from well water is unlikely to be a problem. Radon guide
Between 2023 and 2025 the EPA had 8 town water systems in Shasta 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 16 ng/L of PFOA. Only 7 wells in Shasta 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
Questions people ask about well water in Shasta County
Is well water in Shasta County safe to drink?
Most tested wells in Shasta County came in under the limits. Of 7 health checks with enough tests, manganese came closest, at 2 of 58 wells over. Every well is different, so test yours for bacteria, nitrate and arsenic.
Can I get my well tested for free in Shasta 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 Shasta County.
How deep are wells in Shasta County?
Half the household wells here are shallower than 160 feet. Typical household wells here are shallower than in 42 of the 56 other California counties with enough drilling records.
How does Shasta County compare with the counties around it?
For manganese, the share of tested wells over the limit: 3 of the 4 neighboring counties with data had a higher share than Shasta County, at 3%. Modoc had the most, at 8%. Groundwater doesn't stop at county lines, so Modoc's 8% is worth knowing about if you live near it.
How often should I test my well in Shasta County?
In Shasta County, 5 of 37 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.
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Where the Shasta County numbers come from
- People on wells: 37,596 in Shasta County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 599 well water samples from 60 wells in the Water Quality Portal, run by the USGS and EPA, 2007 to 2022.
- Well depths: 11,941 California drilling records for Shasta County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Shasta County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 8 town water systems in Shasta County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Shasta County is zone 3 on the EPA Map of Radon Zones.
- State programs and links: State Water Resources Control Board, checked November 1, 2026.