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Sonora Meadows Mutual WTR Co

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
1,123 people
Connections
451
Water source
Surface water bought from another system
Based in
Sonora, CA
County
Tuolumne
Owner
Private
Hardness
Varies by source
The ZIP code it serves

95370

The short answer

2 results are above the health goal. The worst: Uranium, above the health goal. 1 health-based violation since 2016.

What handles it

What was found

Uranium, arsenic, haloacetic acids (HAA5), total trihalomethanes (TTHM), fluoride, nitrate and chromium (total): California’s own results, samples taken from March 10, 2020 to June 30, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal2

Uranium

Comes from the source

Above the health goal

8.0ppb

Highest yearly average, 2020

Averaged by year, the highest was 8.0 ppb, in 2020: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That is the only year on file.

What handles it

Arsenic

Comes from the source

Above the health goal

1.9ppb

Highest yearly average, 2020 to 2023

2023 average: 1.8 ppb

Averaged by year, the highest was 1.9 ppb, in 2020: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 3.5 ppb. In 2023, the latest year on file, its two samples averaged 1.8 ppb.

What handles it

  • NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
  • NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”

Below EPA’s limits5

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

43.3ppb

Highest yearly average, 2020 to 2026

2026 average: 19.5 ppb

Averaged by year, the highest was 43.3 ppb, in 2020, below EPA’s legal limit of 60 ppb. Its highest single sample was 73.9 ppb. In 2026, the latest year on file, its four samples averaged 19.5 ppb. EPA recorded no violation for haloacetic acids (HAA5) at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 58.6 ppb, in 2015, and EPA recorded a violation in 2015.

What handles it

No certification claim covers this compound yet.

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

23.1ppb

Highest yearly average, 2020 to 2026

2026 average: 21.5 ppb

Averaged by year, the highest was 23.1 ppb, in 2020, below EPA’s legal limit of 80 ppb. Its highest single sample was 76 ppb. In 2026, the latest year on file, its two samples averaged 21.5 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 42.3 ppb, in 2016.

What handles it

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

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.85ppm

Highest yearly average, 2020 to 2023

2023 average: 0.3 ppm

Averaged by year, the highest was 0.85 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.87 ppm. In 2023, the latest year on file, its two samples averaged 0.3 ppm.

What handles it

Nitrate

Comes from the source

Below EPA’s limits

1.5ppm

Highest sample; found in 5 of 12

2025 average: 0.33 ppm

The highest sample, in 2024, was 1.5 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its two samples averaged 0.33 ppm.

What handles it

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

Chromium (total)

Comes from the source

Below EPA’s limits

2.8ppb

Highest yearly average, 2020 to 2023

2023: not found

Averaged by year, the highest was 2.8 ppb, in 2020, below EPA’s legal limit of 100 ppb. Its highest single sample was 3.3 ppb. In 2023, the latest year on file, it wasn’t found in any of its two samples.

What handles it

One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Lead

What handles it

A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”

  • NSF/ANSI 53

    Claim: Arsenic (Pentavalent)<=50 ppb Reduction

    For: Arsenic

    Other certifiers’ wording: Arsenic (III) (50 ppb influent level)

  • NSF/ANSI 58

    Claims: Uranium, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Uranium, Arsenic

    Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

At the tap, or for the whole house?

These come with the water itself, so a whole-house system certified for the same claims treats every tap and shower. A filter at the tap treats drinking water for much less. How whole-house systems compare.

Filters with those claims on a certifier’s listing

Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

Compare five-year costs

The best reverse osmosis systems, ranked

Hardness

Soft to moderately hard depending on the source, 39 to 89 mg/L (2.3 to 5.2 grains per gallon), across 2 sampling points, 2020 to 2023.

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
Lead and Copper Rule RevisionsThe required inventory of lead service lines was not completed or submitted on time.EPA: LSL InventoryOct. 17, 2024—Unaddressed
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 3 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Uranium, arsenic, haloacetic acids (HAA5), total trihalomethanes (TTHM), fluoride, nitrate and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Sonora Meadows Mutual WTR Co’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 March 10, 2020 to June 30, 2026.

Testing your own tap

Sonora Meadows Mutual WTR Co’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 3 labs California certifies closest to the area Sonora Meadows Mutual WTR Co serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Precision Enviro-Tech

    Twain Harte, CA · about 8 miles

    Certified for bacteria

    (209) 477-8105

  • 49er Water Laboratory

    Jackson, CA · about 34 miles

    Certified for bacteria, nitrate, minerals and other inorganics

    (530) 277-2770

  • Aemtek, Inc.

    Modesto, CA · about 41 miles

    Certified for bacteria

    (510) 979-1979

All 145 certified labs for California

Sources

PWSID CA5510023. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Tuolumne County

All California utilities

What to do next