Willow Creek C.S.D.
What EPA’s and California’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.
- Serves
- 1,720 people
- Connections
- 942
- Water source
- Groundwater influenced by surface water
- Based in
- Willow Creek, CA
- County
- Humboldt
- Owner
- Local government
- Hardness
- Moderately hard
The short answer
Nothing in EPA’s and California’s records for this utility is above a health goal. That covers nitrate, arsenic and other regulated chemicals, plus lead and copper, not everything. 2 health-based violations since 2016.
What was found
Haloacetic acids (HAA5), total trihalomethanes (TTHM), chromium (total), nitrate, arsenic and fluoride: California’s own results, samples taken from June 22, 2020 to Sept. 24, 2025, with EPA’s 2012 to 2019 file for earlier years.
Below EPA’s limits4
Haloacetic acids (HAA5)
Forms or is added in treatment
28.2ppb
Highest yearly average, 2021 to 2025
2025, one sample: 22 ppb
Averaged by year, the highest was 28.2 ppb, in 2022, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, its one sample was 22 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 28 ppb, in 2019.
What handles it
No certification claim covers this compound yet.
Total trihalomethanes (TTHM)
Forms or is added in treatment
23.3ppb
Highest yearly average, 2021 to 2025
2025, one sample: 21 ppb
Averaged by year, the highest was 23.3 ppb, in 2022, below EPA’s legal limit of 80 ppb. In 2025, the latest year on file, its one sample was 21 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 20 ppb, in 2019.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Chromium (total)
Comes from the source
2.5ppb
Highest yearly average, 2022 to 2024
2024: not found
Averaged by year, the highest was 2.5 ppb, in 2022, below EPA’s legal limit of 100 ppb. In 2024, the latest year on file, it wasn’t found in its one sample.
What handles it
- NSF/ANSI 58 look for “Chromium (Hexavalent) Reduction”
- NSF/ANSI 53 look for “Chromium Reduction”
Nitrate
Comes from the source
0.23ppm
Highest sample; found in 3 of 6
2025, one sample: 0.12 ppm
The highest sample, in 2024, was 0.23 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its one sample was 0.12 ppm.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Fluoride
- Lead
Hardness
Moderately hard, typically 93 mg/L (5.4 grains per gallon), across 2 sampling points, 2022 to 2024.
Hardness is calcium and magnesium. EPA sets no limit for it: it shows up as scale on fixtures and in water heaters, and as soap that won’t lather. USGS calls water above 60 mg/L moderately hard, above 120 hard and above 180 very hard.
Violations since 2016
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Lead and Copper Rule Revisions | The required inventory of lead service lines was not completed or submitted on time.EPA: LSL Inventory | Oct. 17, 2024 | — | Unaddressed |
| Revised Total Coliform Rule | Coliform results required a check of the system, and the check or its fixes were not done on time.EPA: Treatment Technique, Level 1 Assessment (RTCR) | June 18, 2019 | — | Resolved |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 2 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Haloacetic acids (HAA5), total trihalomethanes (TTHM), chromium (total), nitrate, arsenic and fluoride results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Willow Creek C.S.D.’s own annual report, which it must send you every year, has the contaminants this page does not show.
Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.
What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.
Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; California’s results run from June 22, 2020 to Sept. 24, 2025.
Testing your own tap
The 3 labs California certifies closest to the area Willow Creek C.S.D. serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Microbac Laboratories, Inc. - Arcata
Arcata, CA · about 25 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts
Humboldt County Public Health Laboratory
Eureka, CA · about 31 miles
Certified for bacteria
Pace Analytical Services, LLC - Redding
Redding, CA · about 66 miles
Certified for bacteria
Sources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- California State Water Resources Control Board, Division of Drinking Water, results from Jan. 1, 2020 to July 17, 2026, read Oct. 8, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: California State Water Resources Control Board, ELAP accredited laboratories and their fields of accreditation, read Oct. 17, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Hardness: California State Water Resources Control Board, Division of Drinking Water, results from March 3, 2022 to April 10, 2024, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA1210015. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Nothing here is above a health goalIn EPA’s and California’s records for this utility. They don’t cover everything, which is why the next step matters.Every contaminant TapBuff tracks
- Get the utility’s own reportWillow Creek C.S.D. must send you a water quality report every year. It covers contaminants this page does not show.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Decide if you want a filter at allA filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.NSF/ANSI standards, decoded