Manganese is widespread in Santa Cruz County wells.
1 widespread, 1 worth checking, 5 rare out of 7 health checks.
From 38 wells tested in Santa Cruz County since 2005; 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 7 people 40,932 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)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how Santa Cruz County compares with California and the counties around it.
Each result puts Santa Cruz County next to the 4 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Santa Cruz County wells.
Manganese6 of 38 wells over
This one is worth checking in Santa Cruz County.
Arsenic2 of 37 wells over
These 5 are rare in Santa Cruz County.
Nitrate0 of 38 wells over
Uranium0 of 38 wells over
Radon in water0 of 31 wells over
Too few tested to show: San Benito, San Mateo.
Fluoride0 of 38 wells over
Lead0 of 38 wells over
Coliform bacteria turned up in 1 of 9 tested Santa Cruz County wells, so test for it every year.
Coliform bacteria1 of 9 wells had it
E. coli0 of 9 wells had it
E. coli means human or animal waste is getting in, so if a test of your Santa Cruz County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 10 of 38 tested wells, and it isn't a health risk.
Iron stains10 of 38 wells had it
Santa Cruz County has 38 tested wells, and the busiest decade for testing was the 2010s.
Only 11 of the 38 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Santa Cruz 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 4 things to check in Santa Cruz County.
- Bacteria
- Nitrate
- Manganese
- 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 245 feet.
That comes from 4,840 household wells in California's drilling records. Most wells of every kind here are 120 to 340 feet deep. Wells as deep as Santa Cruz 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 go deeper than in 39 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 Santa Cruz County.
Santa Cruz County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide
Between 2023 and 2025 the EPA had 8 town water systems in Santa Cruz 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 6.5 ng/L of PFOA. Only 11 wells in Santa Cruz 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 Santa Cruz County
Is well water in Santa Cruz County safe to drink?
6 of 38 wells tested in Santa Cruz County had manganese over the limit, about 2 in 10. Across California it's about 1 in 12. That's a bigger share than in 33 of the 45 other California counties with 10 or more tested wells. So test your own well for manganese before you count on it.
Can I get my well tested for free in Santa Cruz 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, manganese and arsenic, the tests that matter most in Santa Cruz County.
How deep are wells in Santa Cruz County?
Half the household wells here are shallower than 245 feet. Typical household wells here go deeper than in 39 of the 56 other California counties with enough drilling records.
How does Santa Cruz County compare with the counties around it?
For manganese, the share of tested wells over the limit: 2 of the 4 neighboring counties with data had a higher share than Santa Cruz County, at 16%. San Mateo had the most, at 25%. Groundwater doesn't stop at county lines, so San Mateo's 25% is worth knowing about if you live near it.
How often should I test my well in Santa Cruz County?
In Santa Cruz County, 1 of 9 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 Santa Cruz County numbers come from
- People on wells: 40,932 in Santa Cruz County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 478 well water samples from 38 wells in the Water Quality Portal, run by the USGS and EPA, 2005 to 2023.
- Well depths: 4,840 California drilling records for Santa Cruz County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 4 counties that share a border with Santa Cruz County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 8 town water systems in Santa Cruz County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Santa Cruz County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: State Water Resources Control Board, checked November 1, 2026.