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Rockport Colony

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
92 people
Connections
10
Water source
Groundwater
Based in
Pendroy, MT
County
Teton
Owner
Private
The ZIP code it serves

59467

The short answer

3 results are above the health goal. The worst: Arsenic, above the health goal. 1 health-based violation since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 1996 to 2026.

Copper: EPA’s file records a utility’s copper only when it exceeds the action level. The last here was 1.7 ppm, for the period ending Dec. 31, 1999. None since is on file, so it is not counted as a current finding.

Arsenic, uranium, fluoride, nitrate, chromium (total) and total trihalomethanes (TTHM): Montana’s own results, samples taken from Jan. 14, 2020 to March 17, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal3

Arsenic

Comes from the source

Above the health goal

9.0ppb

Highest yearly average, 2020 to 2026

2026, one sample: 7.0 ppb

Averaged by year, the highest was 9.0 ppb, in 2021: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2026, the latest year on file, its one sample was 7.0 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 12 ppb, in 2012, and EPA recorded a violation in 2012.

What handles it

  • NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
  • NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”

Lead

Comes from pipes, often your own

Above the health goal

2.0ppb

90th percentile, 2024 to 2026

In the latest period, 9 in 10 homes sampled were at or below 2.0 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

Uranium

Comes from the source

Above the health goal

2.0ppb

Highest yearly average, 2020 to 2026

2026, one sample: 1.8 ppb

Averaged by year, the highest was 2.0 ppb, in 2020: below EPA’s legal limit of 30 ppb, but above its health goal of zero. In 2026, the latest year on file, its one sample was 1.8 ppb.

What handles it

Below EPA’s limits3

Fluoride

Forms or is added in treatment

Below EPA’s limits

1.7ppm

Highest yearly average, 2020 to 2026

2026, one sample: 1.5 ppm

Averaged by year, the highest was 1.7 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 1.5 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.6 ppm, in 2017.

What handles it

Nitrate

Comes from the source

Below EPA’s limits

3.0ppm

Highest sample; found in 7 of 7

2026, one sample: 0.03 ppm

The highest sample, in 2022, was 3.0 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 0.03 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 26.8 ppm, in 2018, and EPA recorded violations in 2012 and 2018.

What handles it

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

Chromium (total)

Comes from the source

Below EPA’s limits

8.0ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 8.0 ppb, in 2025, below EPA’s legal limit of 100 ppb. In 2026, the latest year on file, it wasn’t found in its one sample.

What handles it

One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Total trihalomethanes (TTHM)

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: Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Arsenic, Lead

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

  • NSF/ANSI 58

    Claims: Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction, Uranium

    For: Arsenic, Lead, Uranium

    Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

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 reverse osmosis systems, ranked

The best water filters for lead, ranked

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Nitrate-NitriteA 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, 201814.6 MG/LResolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 2 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Arsenic, uranium, fluoride, nitrate, chromium (total) and total trihalomethanes (TTHM) results here are Montana’s own from 2020 on, with EPA’s national file for 2012 to 2019. Rockport Colony’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 Jan. 14, 2020 to March 17, 2026.

Testing your own tap

Rockport Colony’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 Rockport Colony 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

Sources

PWSID MT0001778. Rebuilt from EPA data on Oct. 18, 2026.

Also in Teton County

All Montana utilities

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