Colusa Co. Service Area #1 - Century Ranch

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: 450 people
Connections: 161
Water source: Surface water
Based in: Colusa, CA
County: Colusa
Owner: Private
Hardness: Varies by source

The ZIP code it serves

95932

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. No health-based violations on file since 2016.

What was found

Total trihalomethanes (TTHM), fluoride, haloacetic acids (HAA5), chromium (total), nitrate, arsenic and uranium: California’s own results, samples taken from July 16, 2020 to Aug. 21, 2025, with EPA’s 2012 to 2019 file for earlier years.

Below EPA’s limits5

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

49ppb

Highest yearly average, 2020 to 2025

2025 average: 5.3 ppb

Averaged by year, the highest was 49 ppb, in 2022, below EPA’s legal limit of 80 ppb. In 2025, the latest year on file, its three samples averaged 5.3 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 48 ppb, in 2019.

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

0.5ppm

Highest yearly average, 2021 to 2024

2024: not found

Averaged by year, the highest was 0.5 ppm, in 2022, below EPA’s legal limit of 4.0 ppm. In 2024, the latest year on file, it wasn’t found in any of its two samples. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.3 ppm, in 2019.

What handles it

NSF/ANSI 58 look for “Fluoride Reduction”
NSF/ANSI 53 look for “Fluoride”

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

4.7ppb

Highest yearly average, 2020 to 2025

2025: not found

Averaged by year, the highest was 4.7 ppb, in 2020, below EPA’s legal limit of 60 ppb. In 2025, 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 10 ppb, in 2019.

What handles it

No certification claim covers this compound yet.

Chromium (total)

Comes from the source

Below EPA’s limits

7.0ppb

Highest yearly average, 2021 to 2024

Averaged by year, the highest was 7.0 ppb, in 2024, below EPA’s legal limit of 100 ppb. Its highest single sample was 14 ppb. That was also the latest year on file.

What handles it

NSF/ANSI 58 look for “Chromium (Hexavalent) Reduction”
NSF/ANSI 53 look for “Chromium Reduction”

Nitrate

Comes from the source

Below EPA’s limits

0.4ppm

Highest sample; found in 1 of 25

2025: not found

The highest sample, in 2024, was 0.4 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, it wasn’t found in any of its four samples. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.14 ppm, in 2015.

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
Lead
Uranium

Hardness

Soft to very hard depending on the source, 49 to 554 mg/L (2.8 to 32.4 grains per gallon), across 3 sampling points, 2019 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.

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

Violations since 2016

No health-based violations on file with EPA since 2016. There are 4 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

Everything else. Total trihalomethanes (TTHM), fluoride, haloacetic acids (HAA5), chromium (total), nitrate, arsenic and uranium results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Colusa Co. Service Area #1 - Century Ranch’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 July 16, 2020 to Aug. 21, 2025.

Testing your own tap

Colusa Co. Service Area #1 - Century Ranch’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 Colusa Co. Service Area #1 - Century Ranch 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 34 miles
Certified for bacteria
(530) 343-5818
Cranmer Engineering, Inc.
Grass Valley, CA · about 50 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics
(530) 273-7284
Eurofins Sacramento Service Center
West Sacramento, CA · about 52 miles
Certified for bacteria, nitrate, minerals and other inorganics
(626) 386-1221