City of Boulder
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
- 1,400 people
- Connections
- 563
- Water source
- Groundwater
- Based in
- Boulder, MT
- County
- Jefferson
- Owner
- Local government
The ZIP code it serves
The short answer
1 result is above the health goal. The worst: Uranium, above the health goal. 1 health-based violation since 2016.
What handles itWhat was found
Copper: EPA’s file records a utility’s copper only when it exceeds the action level. The last here was 1.4 ppm, for the period ending June 30, 2009. None since is on file, so it is not counted as a current finding.
Uranium, total trihalomethanes (TTHM), nitrate, fluoride, haloacetic acids (HAA5), arsenic and chromium (total): Montana’s own results, samples taken from Aug. 14, 2020 to Sept. 16, 2026, with EPA’s 2012 to 2019 file for earlier years.
Above the health goal1
Uranium
Comes from the source
8.3ppb
Highest yearly average, 2022 to 2025
2025, one sample: 4.0 ppb
Averaged by year, the highest was 8.3 ppb, in 2022: below EPA’s legal limit of 30 ppb, but above its health goal of zero. Its highest single sample was 9.2 ppb. In 2025, the latest year on file, its one sample was 4.0 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 5.0 ppb, in 2016.
What handles it
- NSF/ANSI 58 look for “Uranium”
Below EPA’s limits4
Total trihalomethanes (TTHM)
Forms or is added in treatment
6.8ppb
Highest yearly average, 2020 to 2026
Averaged by year, the highest was 6.8 ppb, in 2026, below EPA’s legal limit of 80 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 4.4 ppb, in 2015.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Nitrate
Comes from the source
0.63ppm
Highest sample; found in 2 of 2
2025 average: 0.55 ppm
The highest sample, in 2025, was 0.63 ppm, below EPA’s legal limit of 10 ppm. That is the only year on file, and its two samples averaged 0.55 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 1.1 ppm, in 2013.
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
0.25ppm
Highest yearly average, 2022 to 2025
Averaged by year, the highest was 0.25 ppm, in 2025, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.3 ppm. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.2 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
3.2ppb
Highest yearly average, 2020 to 2026
2026, one sample: 1.1 ppb
Averaged by year, the highest was 3.2 ppb, in 2020, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its one sample was 1.1 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 3.5 ppb, in 2018.
What handles it
No certification claim covers this compound yet.
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Chromium (total)
- 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 58
Claim: Uranium
For: Uranium
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
None of the filters TapBuff has checked so far carry these claims. Search the certifier listings for the claim above.
Compare five-year costsViolations since 2016
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Surface Water Treatment Rule | Water drawn from a river, lake or reservoir was not filtered as required.EPA: Failure to Filter (SWTR) | July 1, 2022 | — | Resolved |
| 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, total trihalomethanes (TTHM), nitrate, fluoride, haloacetic acids (HAA5), arsenic and chromium (total) results here are Montana’s own from 2020 on, with EPA’s national file for 2012 to 2019. City of Boulder’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 Aug. 14, 2020 to Sept. 16, 2026.
Testing your own tap
The 3 labs Montana certifies closest to the area City of Boulder serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
DPHHS State of Montana Environmental Laboratory
Helena, MT · about 24 miles
Certified for bacteria, minerals and other inorganics, organic chemicals
Alpine Analytical
Helena, MT · about 24 miles
Certified for bacteria, minerals and other inorganics
Montana Bureau of Mines and Geology
Butte, MT · about 25 miles
Certified for minerals and other inorganics
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 MontanaSources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- Montana Department of Environmental Quality, Public Water Supply, results from Jan. 2, 2020 to Oct. 6, 2026, read Oct. 18, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: Montana Department of Public Health and Human Services, Water Laboratory Certification Program, certified laboratories, read Oct. 10, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID MT0000158. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on UraniumWhat each one does to health, where it comes from, and the certification claim that addresses it.About Uranium
- Get the utility’s own reportCity of Boulder must send you a water quality report every year. It covers contaminants this page does not show.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Compare certified filtersWhat the filters certified for these results cost over five years, cartridges included.Compare five-year costs