Public water system · 083090010
ActiveSt Mary Koa
At a glance
St Mary Koa (PWSID 083090010) is an active transient non-community water system in Montana. It reports serving 700 people through 211 service connections. Its primary water source is groundwater, and EPA lists it as Native American-owned. EPA's records list 3 violations for this system; 1 is health-based, and the most recent began in May 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
700
Service connections
211
Primary source
GW
Groundwater
System type
TNCWS
Transient non-community water system
System record
How does St Mary Koa compare with other water systems in Montana?
By EPA's size categories, St Mary Koa is a small system (501 to 3,300 people). Across Montana, the 2,378 active systems average 489 people each. Nationally, the average active transient non-community water system reports serving 144 people, so St Mary Koa is about 4.9 times that figure.
What does “transient non-community water system” mean?
A transient non-community water system serves places where people do not stay long, such as gas stations and campgrounds, and regularly serves at least 25 people a day for at least 60 days a year. Montana has 1,206 active transient non-community water systems, 51% of the state's 2,378 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 1,994 Montana systems (84%) list groundwater as their primary source.
Who owns and regulates St Mary Koa?
EPA lists St Mary Koa as Native American-owned. The EPA Region 08 is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act.
Does St Mary Koa have drinking water violations?
EPA's records list 3 violations for this system; 1 is health-based, and the most recent began in May 2025. The violations listed here began between April 2012 and May 2025. By type: 2 monitoring and reporting and 1 required treatment not met. The contaminant or rule involved most often is Total coliform bacteria (TCR) (2 of them). EPA lists 3 as resolved. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2025-05-01 | Required treatment not metTreatment Technique Startup Procedures (RTCR) · code 2D | Revised Total Coliform Rulecode 8000 | Yes | Resolved |
| 2013-07-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2012-04-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
All 3 violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
St Mary Koa: frequently asked questions
Who runs St Mary Koa?
St Mary Koa (PWSID 083090010) is a transient non-community water system Native American-owned. It is regulated by the EPA Region 08.
How many people does St Mary Koa serve?
St Mary Koa reports serving 700 people through 211 service connections in Montana.
Where does St Mary Koa get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does St Mary Koa have any drinking water violations?
EPA's records list 3 violations for this system; 1 is health-based, and the most recent began in May 2025. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is St Mary Koa's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. EPA's records list 3 violations for this system; 1 is health-based, and the most recent began in May 2025. For current results, consult EPA ECHO, or the EPA Region 08.
Where can I find St Mary Koa's water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. St Mary Koa is a transient non-community water system, so it is not required to publish one; like every public water system, it must notify the people it serves about violations under EPA's public notification rules.
Other water systems in Montana
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Billings City of | Yellowstone | 114,000 | Community | Surface water |
| Missoula Water | Missoula | 68,200 | Community | Groundwater |
| Great Falls City of | Cascade | 60,000 | Community | Surface water |
| Bozeman City of | Gallatin | 56,000 | Community | Surface water |
| Butte Silverbow Water Dept | Silver Bow | 33,000 | Community | Surface water |
| Helena Water System | Lewis and Clark | 32,091 | Community | Surface water |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “St Mary Koa, PWSID 083090010, Montana”, https://aquacensus.com/water-systems/montana/st-mary-koa-083090010 (data as of October 1, 2026).