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Twin Hills Colony Inc

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
78 people
Connections
19
Water source
Surface water bought from another system
Based in
Carter, MT
County
Chouteau
Owner
Private

The short answer

2 results are above EPA’s legal limit. The worst: Haloacetic acids (HAA5), above the legal limit. 8 health-based violations since 2016.

What handles it

What was found

Haloacetic acids (HAA5) and total trihalomethanes (TTHM): Montana’s own results, samples taken from March 18, 2020 to Aug. 10, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit2

Haloacetic acids (HAA5)

Forms or is added in treatment

Above the legal limit

59ppb

Highest yearly average, 2020 to 2026

2026 average: 50.3 ppb

Averaged by year, the highest was 59 ppb, in 2023, below EPA’s legal limit of 60 ppb. Its highest single sample was 72 ppb. In 2026, the latest year on file, its three samples averaged 50.3 ppb. EPA judges this limit at each sampling point, and recorded a violation for haloacetic acids (HAA5) at this utility in 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 106 ppb, in 2018, and EPA recorded a violation in 2019.

What handles it

No certification claim covers this compound yet.

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the legal limit

76.3ppb

Highest yearly average, 2020 to 2026

2026 average: 56.3 ppb

Averaged by year, the highest was 76.3 ppb, in 2020, below EPA’s legal limit of 80 ppb. Its highest single sample was 91 ppb. In 2026, the latest year on file, its three samples averaged 56.3 ppb. EPA judges this limit at each sampling point, and recorded a violation for total trihalomethanes (TTHM) at this utility in 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 88 ppb, in 2018, and EPA recorded a violation in 2019.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • 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 53

    Claim: Trihalomethanes (TTHM) Reduction

    For: Total trihalomethanes (TTHM)

    Other certifiers’ wording: VOC Reduction

  • NSF/ANSI 58

    Claim: Trihalomethanes (TTHM) Reduction

    For: Total trihalomethanes (TTHM)

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

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

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2020 to Sept. 30, 202065 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2020 to June 30, 202081.8 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2020 to March 31, 202092 UG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2020 to March 31, 202073 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2019 to Dec. 31, 201994 UG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2019 to Dec. 31, 201981 UG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2019 to Sept. 30, 201974 UG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2019 to Sept. 30, 2019108 UG/LResolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 15 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Haloacetic acids (HAA5) and total trihalomethanes (TTHM) results here are Montana’s own from 2020 on, with EPA’s national file for 2012 to 2019. Twin Hills Colony Inc’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 March 18, 2020 to Aug. 10, 2026.

Testing your own tap

Twin Hills Colony Inc’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 Twin Hills Colony Inc 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 MT0003978. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Chouteau County

All Montana utilities

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