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Del Oro Water Co. - Stirling Bluffs

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
512 people
Connections
155
Water source
Surface water
Based in
Chico, CA
County
Butte
Owner
Private
The 2 ZIP codes it serves

95954, 95978

The short answer

1 result is above the limit’s level with no violation recorded, and 1 more is above the health goal. The worst: Total trihalomethanes (TTHM), above the limit’s level, no violation. No health-based violations on file since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2005 to 2026.

Total trihalomethanes (TTHM), haloacetic acids (HAA5) and nitrate: California’s own results, samples taken from April 28, 2020 to Sept. 16, 2025, with EPA’s 2012 to 2019 file for earlier years.

Arsenic, chromium (total) and fluoride: EPA’s compliance monitoring file, samples taken from Nov. 21, 2017 to Nov. 21, 2017. Newer results are in the utility’s annual water quality report.

Above the limit’s level, no violation recorded1

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the limit’s level, no violation

93.5ppb

Highest yearly average, 2020 to 2025

2025, one sample: 30.6 ppb

Averaged by year, the highest was 93.5 ppb, in 2024, above EPA’s legal limit of 80 ppb. Its highest single sample was 110 ppb. In 2025, the latest year on file, its one sample was 30.6 ppb. EPA judges this limit on running averages at each sampling point, and recorded no violation for total trihalomethanes (TTHM) at this utility since 2020. Results like these with no violation often include water sampled before treatment or blending; the utility’s annual report says what reaches the tap. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 25 ppb, in 2015.

What handles it

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

Above the health goal1

Lead

Comes from pipes, often your own

Above the health goal

4.5ppb

90th percentile, 2024 to 2026

In the latest period, 9 in 10 homes sampled were at or below 4.5 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.

What handles it

Below EPA’s limits1

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

24.8ppb

Highest yearly average, 2020 to 2025

2025, one sample: 12 ppb

Averaged by year, the highest was 24.8 ppb, in 2023, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, its one sample was 12 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 22 ppb, in 2015.

What handles it

No certification claim covers this compound yet.

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

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: Trihalomethanes (TTHM) Reduction, Lead Reduction

    For: Total trihalomethanes (TTHM), Lead

    Other certifiers’ wording: VOC Reduction

  • NSF/ANSI 58

    Claims: Trihalomethanes (TTHM) Reduction, Lead Reduction

    For: Total trihalomethanes (TTHM), Lead

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. 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 water filters for lead, ranked

Violations since 2016

No health-based violations on file with EPA since 2016.

What this report can’t tell you

  • Everything else. Total trihalomethanes (TTHM), haloacetic acids (HAA5) and nitrate results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Arsenic, chromium (total) and fluoride come from EPA’s file alone, which ends in 2019. Del Oro Water Co. - Stirling Bluffs’s own annual report, which it must send you every year, has newer results for those and 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 April 28, 2020 to Sept. 16, 2025; EPA’s compliance samples are from Nov. 21, 2017 to Nov. 21, 2017.

Testing your own tap

Del Oro Water Co. - Stirling Bluffs’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 Del Oro Water Co. - Stirling Bluffs serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Fruit Growers Laboratory, Inc.

    Chico, CA · about 18 miles

    Certified for bacteria

    (530) 343-5818

  • Cranmer Engineering, Inc.

    Grass Valley, CA · about 53 miles

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

    (530) 273-7284

  • Pace Analytical Services, LLC - Redding

    Redding, CA · about 65 miles

    Certified for bacteria

    (530) 999-4051

All 145 certified labs for California

Sources

PWSID CA0410018. Rebuilt from EPA data on Oct. 18, 2026.

Also in Butte County

All California utilities

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