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Community Water System · PWS MT0000341

Thompson Falls City Of

Thompson Falls, Montana 59813 - drinking water served from groundwater sources to 1,950 people, tracked in EPA SDWIS and UCMR5.

1,950
People served
38
EPA violations
3
Health-based
Untested
UCMR5 result

The verdict

EPA records 38 drinking-water violations at Thompson Falls City Of, 8% of them health-based - below the Montana per-system average.

38
Total EPA violations on record
8%
Health-based (MCL / treatment failure)
1,950
People served by this system
N/A
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Thompson Falls City Of

Thompson Falls City Of is a local-owned community water system that delivers drinking water to 1,950 residents in Thompson Falls, Montana (Sanders County) through 719 service connections. Its water is drawn from groundwater sources. EPA's Safe Drinking Water Information System records 38 total violations for this system , of which 3 (8%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 30 monitoring and reporting violations are on file. The most recent violation on record dates to 2015.

The most frequently cited contaminant at this system is Coliform (TCR), recorded in 8 violations (MR). This system has not yet been sampled under EPA's UCMR5 PFAS monitoring program, so no PFAS detection data is available here.

Across Montana, EPA tracks 2,263 public water systems serving 1,112,267 people, with 297,270 cumulative violations and 25,922 health-based violations on record. About 95% of systems in the state carry at least one violation, and state-wide the average per system is 131.4 violations. Statewide, 28 of 45 UCMR5-tested systems have reported PFAS detections (62.2%).

Thompson Falls City Of's 38 violations sit below the Montana average.

All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

Population Served
1,950
Total Violations
38
Health-Based Violations
3
Water Source
Groundwater

System Details

System Type
Community
Owner Type
Local
Connections
719
County
Sanders
School/Daycare
No
MCL Violations
0
Monitoring Violations
30
Treatment Tech Violations
3

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Coliform (TCR) MR 8 2005
Surface Water Treatment Rule TT 3 1999
Nitrate MR 3 1996
Fluoride MR 2 1994
Selenium MR 2 1994
Mercury MR 2 1994
Chromium MR 2 1994
Barium MR 2 1994
Cadmium MR 2 1994
Arsenic MR 2 1994
Consumer Confidence Rule Other 2 2015
Thallium, Total MR 1 1994
Antimony, Total MR 1 1994
CYANIDE MR 1 1994
Beryllium, Total MR 1 1994
Nickel MR 1 1994

Verify This Water System

The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Thompson Falls City Of.

Federal Source of Truth

EPA SDWIS, Federal Reports

EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:

View PWS ID MT0000341 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

Montana Drinking Water Authority

Montana's primacy agency administers the Safe Drinking Water Act locally. Search EPA SDWIS for the current state contact, or use the state's public health or environment department portal.

Find MT regulator via EPA SDWIS

Violation Timeline

Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.

Year (latest) Contaminant Category Count EPA Record
2015 Consumer Confidence Rule Other 2 SDWIS / MT0000341 / 7000
2005 Coliform (TCR) MR 8 SDWIS / MT0000341 / 3100
1999 Surface Water Treatment Rule TT 3 SDWIS / MT0000341 / 0200
1996 Nitrate MR 3 SDWIS / MT0000341 / 1040
1994 Fluoride MR 2 SDWIS / MT0000341 / 1025
1994 Selenium MR 2 SDWIS / MT0000341 / 1045
1994 Mercury MR 2 SDWIS / MT0000341 / 1035
1994 Chromium MR 2 SDWIS / MT0000341 / 1020
1994 Barium MR 2 SDWIS / MT0000341 / 1010
1994 Cadmium MR 2 SDWIS / MT0000341 / 1015
1994 Arsenic MR 2 SDWIS / MT0000341 / 1005
1994 Thallium, Total MR 1 SDWIS / MT0000341 / 1085
1994 Antimony, Total MR 1 SDWIS / MT0000341 / 1074
1994 CYANIDE MR 1 SDWIS / MT0000341 / 1024
1994 Beryllium, Total MR 1 SDWIS / MT0000341 / 1075

How Thompson Falls City Of Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric Thompson Falls City Of Montana avg Federal benchmark
Total violations 38 131.4 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 3 11.5 Indicates a contaminant exceeded a federal MCL
PFAS detection None 62.2% EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 1,950 492 Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 2,263 regulated public water systems in Montana.

Federal MCL reference, Safe Drinking Water Act thresholds ▼
Contaminant Federal MCL / Action Level Note
Lead 0 mg/L (Action Level: 0.015 mg/L) Lead and Copper Rule treatment technique
Arsenic 0.010 mg/L (10 ppb) Health-based MCL since 2006
Total Coliform Treatment technique (RTCR) Indicator organism, monitoring trigger
PFOA / PFOS (PFAS) 4.0 ppt each (final 2024 rule) Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026)
Nitrate (as N) 10 mg/L Acute health risk for infants

Frequently Asked Questions

Is Thompson Falls City Of water safe to drink? ▼
Thompson Falls City Of (PWS ID: MT0000341) has 38 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 1,950 people using Groundwater sources.
How many people does Thompson Falls City Of serve? ▼
Thompson Falls City Of serves 1,950 people in Thompson Falls, Montana. It is a Local-owned system using Groundwater water sources with 719 service connections.
What type of violations does Thompson Falls City Of have? ▼
Thompson Falls City Of has 38 total violations: 3 health-based violations (MCL exceedances or treatment failures), 30 monitoring/reporting violations, and 3 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Thompson Falls City Of water? ▼
No PFAS testing data is available for Thompson Falls City Of under the EPA's UCMR5 monitoring program.
What water source does Thompson Falls City Of use? ▼
Thompson Falls City Of uses Groundwater as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.
Where does this data come from? ▼
All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. This data is provided for informational purposes only.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.