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San Miguel WS #01

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
100 people
Connections
34
Water source
Groundwater
Based in
Royal Oaks, CA
County
Monterey
Owner
Private
Hardness
Varies by source
The ZIP code it serves

95076

The short answer

1 result is above EPA’s legal limit, and 1 more is above the health goal. The worst: Nitrate, above the legal limit. 18 health-based violations since 2016.

What handles it

What was found

Nitrate, arsenic, chromium (total), fluoride and uranium: California’s own results, samples taken from Sept. 2, 2020 to April 20, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Nitrate

Comes from the source

Above the legal limit

29ppm

Highest sample; found in 24 of 24

2026 average: 1.4 ppm

In 2020, three samples were above EPA’s legal limit of 10 ppm, the highest 29 ppm. Three have no follow-up sample on file within 30 days. In 2026, the latest year on file, its three samples averaged 1.4 ppm. EPA recorded a violation for nitrate at this utility in 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 27 ppm, in 2019, and EPA recorded violations in 2012, 2013, 2014, 2015, 2016, 2017, 2018 and 2019.

What handles it

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

Above the health goal1

Arsenic

Comes from the source

Above the health goal

1.4ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 1.4 ppb, in 2026: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 1.9 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.94 ppb, in 2019.

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 limits2

Chromium (total)

Comes from the source

Below EPA’s limits

17.4ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 17.4 ppb, in 2026, below EPA’s legal limit of 100 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 11 ppb, in 2019.

What handles it

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.11ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.1 ppm

Averaged by year, the highest was 0.11 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 0.1 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.19 ppm, in 2019.

What handles it

2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Lead
  • Uranium

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

    Claims: Nitrate/Nitrite (30 ppm challenge), Arsenic (Pentavalent)<=50 ppb Reduction

    For: Nitrate, Arsenic

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

  • NSF/ANSI 58

    Claims: Nitrate/Nitrite Reduction, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Nitrate, Arsenic

    Other certifiers’ wording: Nitrate; 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

Moderately hard to very hard depending on the source, 82 to 380 mg/L (4.8 to 22.2 grains per gallon), across 2 sampling points, 2019 to 2026.

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
Revised Total Coliform RuleColiform 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)Nov. 18, 2025—Addressed
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2020 to March 31, 202027 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleOct. 1, 2019 to Dec. 31, 201927 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2019 to Sept. 30, 201927 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleApril 1, 2019 to June 30, 201926 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2019 to March 31, 201926 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleOct. 1, 2018 to Dec. 31, 201826 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2018 to Sept. 30, 201826 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleApril 1, 2018 to June 30, 201824 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2018 to March 31, 201824 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleOct. 1, 2017 to Dec. 31, 201723 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2017 to Sept. 30, 201723 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleApril 1, 2017 to June 30, 20170.02 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2017 to March 31, 20170.02 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleOct. 1, 2016 to Dec. 31, 201620 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2016 to Sept. 30, 201620 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleApril 1, 2016 to June 30, 201616 MG/LResolved
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2016 to March 31, 201616 MG/LResolved
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. Nitrate, arsenic, chromium (total), fluoride and uranium results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. San Miguel WS #01’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 Sept. 2, 2020 to April 20, 2026.

Testing your own tap

San Miguel WS #01’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 San Miguel WS #01 serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • CM Analytical, Inc.

    Gilroy, CA · about 12 miles

    Certified for bacteria

    (408) 848-3619

  • Bracewell Engineering, Inc.

    Morgan Hill, CA · about 14 miles

    Certified for bacteria, nitrate, minerals and other inorganics

    (669) 258-5821

  • Santa Cruz County - Health Services Agency - Environmental Health

    Santa Cruz, CA · about 15 miles

    Certified for bacteria

    (831) 454-4624

All 145 certified labs for California

Sources

PWSID CA2700738. Rebuilt from EPA data on Oct. 18, 2026.

Also in Monterey County

All California utilities

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