Public water system · MT0042409
ActiveYellow Bay Flathead Mt St Park
At a glance
Yellow Bay Flathead Mt St Park (PWSID MT0042409) is an active transient non-community water system in Lake County, Montana. It reports serving 25 people through 8 service connections. Its primary water source is groundwater, and EPA lists it as owned by a state government. Of the 12 most recent violations in EPA's records, 4 are health-based, and the most recent began in May 2019.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
25
Service connections
8
Primary source
GW
Groundwater
System type
TNCWS
Transient non-community water system
System record
How does Yellow Bay Flathead Mt St Park compare with other water systems in Lake County?
By EPA's size categories, Yellow Bay Flathead Mt St Park is a very small system (500 people or fewer). Lake County has 90 active public water systems. Its population served is well below the county average of 220 people per system, and accounts for 0.1% of the 19,829 people reported by systems filed under the county. 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 Yellow Bay Flathead Mt St Park is well below 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 Yellow Bay Flathead Mt St Park?
EPA lists Yellow Bay Flathead Mt St Park as owned by a state government. The MT state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 8 of the 90 active systems in Lake County (8.9%) are also owned by a state government.
Does Yellow Bay Flathead Mt St Park have drinking water violations?
Of the 12 most recent violations in EPA's records, 4 are health-based, and the most recent began in May 2019. The violations listed here began between August 2012 and May 2019. By type: 6 monitoring and reporting, 3 required treatment not met, 2 monitoring and 1 contaminant level above the legal limit. The contaminant or rule involved most often is Groundwater Rule (7 of them). EPA lists 12 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 |
|---|---|---|---|---|
| 2019-05-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Groundwater Rulecode 0700 | No | Resolved |
| 2018-08-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Groundwater Rulecode 0700 | No | Resolved |
| 2018-07-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Groundwater Rulecode 0700 | Yes | Resolved |
| 2018-05-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Groundwater Rulecode 0700 | Yes | Resolved |
| 2018-05-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Groundwater Rulecode 0700 | No | Resolved |
| 2018-05-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2017-08-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Groundwater Rulecode 0700 | No | Resolved |
| 2017-07-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Groundwater Rulecode 0700 | No | Resolved |
| 2017-07-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2017-05-02 | Required treatment not metTreatment Technique Startup Procedures (RTCR) · code 2D | Revised Total Coliform Rulecode 8000 | Yes | Resolved |
| 2017-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitrate-Nitritecode 1038 | No | Resolved |
| 2012-08-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
The 12 most recent 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.
Yellow Bay Flathead Mt St Park: frequently asked questions
Who runs Yellow Bay Flathead Mt St Park?
Yellow Bay Flathead Mt St Park (PWSID MT0042409) is a transient non-community water system owned by a state government. It is regulated by the MT state drinking water program.
How many people does Yellow Bay Flathead Mt St Park serve?
Yellow Bay Flathead Mt St Park reports serving 25 people through 8 service connections in Lake County, Montana.
Where does Yellow Bay Flathead Mt St Park 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 Yellow Bay Flathead Mt St Park have any drinking water violations?
Of the 12 most recent violations in EPA's records, 4 are health-based, and the most recent began in May 2019. 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 Yellow Bay Flathead Mt St Park'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. Of the 12 most recent violations in EPA's records, 4 are health-based, and the most recent began in May 2019. For current results, consult EPA ECHO, or the MT state drinking water program.
Where can I find Yellow Bay Flathead Mt St Park's water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. Yellow Bay Flathead Mt St Park 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 Lake County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Polson City of | Lake | 5,300 | Community | Groundwater |
| Ronan City of | Lake | 2,483 | Community | Surface water |
| Pablo Lake County Water and Sewer Dist | Lake | 2,175 | Community | Groundwater |
| St Ignatius Town of | Lake | 700 | Community | Groundwater |
| Woods Bay Water and Sewer District | Lake | 685 | Community | Groundwater |
| Wilson Foods | Lake | 600 | Transient non-community | Groundwater |
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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, “Yellow Bay Flathead Mt St Park, PWSID MT0042409, Montana”, https://aquacensus.com/water-systems/montana/yellow-bay-flathead-mt-st-park-mt0042409 (data as of October 1, 2026).