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Ridgewood Water System

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
265 people
Connections
168
Water source
Groundwater influenced by surface water
Based in
Willits, CA
County
Mendocino
Owner
Private
Hardness
Varies by source
The ZIP code it serves

95490

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. 1 health-based violation since 2016.

What was found

Haloacetic acids (HAA5), total trihalomethanes (TTHM), nitrate, fluoride, arsenic and chromium (total): California’s own results, samples taken from Dec. 3, 2020 to Dec. 29, 2025, with EPA’s 2012 to 2019 file for earlier years.

Below EPA’s limits4

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

17.6ppb

Highest yearly average, 2021 to 2024

2024: not found

Averaged by year, the highest was 17.6 ppb, in 2021, below EPA’s legal limit of 60 ppb. In 2024, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.2 ppb, in 2018.

What handles it

No certification claim covers this compound yet.

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

13.9ppb

Highest yearly average, 2021 to 2024

2024, one sample: 3.0 ppb

Averaged by year, the highest was 13.9 ppb, in 2021, below EPA’s legal limit of 80 ppb. In 2024, the latest year on file, its one sample was 3.0 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 4.0 ppb, in 2015.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”

Nitrate

Comes from the source

Below EPA’s limits

0.63ppm

Highest sample; found in 2 of 14

2025: not found

The highest sample, in 2024, was 0.63 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, it wasn’t found in any of its two samples.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.21ppm

Highest yearly average, 2020 to 2025

2025, one sample: 0.11 ppm

Averaged by year, the highest was 0.21 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.22 ppm. In 2025, the latest year on file, its one sample was 0.11 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.21 ppm, in 2017.

What handles it

3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Arsenic
  • Chromium (total)
  • Lead

Hardness

Moderately hard to hard depending on the source, 112 to 156 mg/L (6.5 to 9.1 grains per gallon), across 4 sampling points, 2019 to 2025.

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.

Softeners compared, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Surface Water Treatment RuleWater drawn from a river, lake or reservoir was not filtered as required.EPA: Failure to Filter (SWTR)June 20, 2023—Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 1 monitoring or reporting violation not shown.

What this report can’t tell you

  • Everything else. Haloacetic acids (HAA5), total trihalomethanes (TTHM), nitrate, fluoride, arsenic and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Ridgewood Water System’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 Dec. 3, 2020 to Dec. 29, 2025.

Testing your own tap

Ridgewood Water System’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab California certifies.

The 2 labs California certifies closest to the area Ridgewood Water System serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Alpha Analytical Laboratories, Inc. - Ukiah

    Ukiah, CA · about 25 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, radioactivity

    (707) 468-0401

  • K Prime, LLC.

    Santa Rosa, CA · about 74 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, PFAS

    (707) 527-7574

All 145 certified labs for California

Sources

PWSID CA2300708. Rebuilt from EPA data on Oct. 18, 2026.

Also in Mendocino County

All California utilities

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