Sunset Colony Unapproved

What EPA’s and Montana’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: 75 people
Connections: 2
Water source: Groundwater bought from another system
Based in: Roundup, MT
County: Musselshell
Owner: Private

The short answer

Nothing in EPA’s and Montana’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

Nitrate, fluoride, arsenic, chromium (total), total trihalomethanes (TTHM) and uranium: Montana’s own results, samples taken from May 29, 2025 to Sept. 16, 2025.

Below EPA’s limits2

Nitrate

Comes from the source

Below EPA’s limits

0.91ppm

One sample

2025, one sample: 0.91 ppm

The highest sample, in 2025, was 0.91 ppm, below EPA’s legal limit of 10 ppm. That is the only year on file, and its one sample was 0.91 ppm.

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

0.2ppm

Highest yearly average, 2025

Averaged by year, the highest was 0.2 ppm, in 2025, below EPA’s legal limit of 4.0 ppm. That is the only year on file.

What handles it

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

5 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.

Arsenic
Chromium (total)
Lead
Total trihalomethanes (TTHM)
Uranium

Violations since 2016

No health-based violations on file with EPA since 2016. There are 2 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

Everything else. Nitrate, fluoride, arsenic, chromium (total), total trihalomethanes (TTHM) and uranium results here are Montana’s own from 2025 on, with EPA’s national file for 2012 to 2019. Sunset Colony Unapproved’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; Montana’s results run from May 29, 2025 to Sept. 16, 2025.

Testing your own tap

Sunset Colony Unapproved’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 Montana certifies.

No lab Montana certifies is within 75 miles of the area Sunset Colony Unapproved serves on the state’s list. Some take samples by mail; the state’s page lists them all.

Montana State Environmental Laboratory: Private well testing packages for bacteria, metals, nutrients, anions, organic chemicals and more, open to the public. Samples can be mailed, sent by the lab's free courier, or dropped off at the lab. Environmental Laboratory, Montana Department of Public Health and Human Services.

All 36 certified labs for Montana