Public water system · MT0004023
ActiveMt Moonlight Basin
At a glance
Mt Moonlight Basin (PWSID MT0004023) is an active community water system in Madison County, Montana. It reports serving 355 people through 408 service connections. Its primary water source is groundwater, and EPA lists it as privately owned. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in January 2008.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
355
Service connections
408
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Mt Moonlight Basin compare with other water systems in Madison County?
By EPA's size categories, Mt Moonlight Basin is a very small system (500 people or fewer). Madison County has 45 active public water systems. Its population served is about 11% above the county average of 320 people per system, and accounts for 2.5% of the 14,392 people reported by systems filed under the county. Across Montana, the 2,378 active systems average 489 people each. Nationally, the average active community water system reports serving 6,703 people, so Mt Moonlight Basin is well below that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Montana has 853 active community water systems, 36% 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 Mt Moonlight Basin?
EPA lists Mt Moonlight Basin as privately owned. 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. 26 of the 45 active systems in Madison County (58%) are also privately owned.
Does Mt Moonlight Basin have drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in January 2008. The violations listed here began between January 2001 and January 2008. By type: 11 monitoring and reporting and 1 contaminant level above the legal limit. The contaminant or rule involved most often is Total coliform bacteria (TCR) (11 of them). EPA lists 11 as resolved and 1 as archived. 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. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Fluoridecode 1025 | No | Archived |
| 2005-12-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2005-10-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2001-10-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2001-09-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2001-07-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2001-06-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2001-04-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2001-03-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2001-02-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Resolved |
| 2001-01-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | 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.
Mt Moonlight Basin: frequently asked questions
Who runs Mt Moonlight Basin?
Mt Moonlight Basin (PWSID MT0004023) is a community water system privately owned. It is regulated by the MT state drinking water program.
How many people does Mt Moonlight Basin serve?
Mt Moonlight Basin reports serving 355 people through 408 service connections in Madison County, Montana.
Where does Mt Moonlight Basin 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 Mt Moonlight Basin have any drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in January 2008. 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 Mt Moonlight Basin'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, one is health-based, and the most recent began in January 2008. For current results, consult the system's annual water quality report, EPA ECHO, or the MT state drinking water program.
Where can I find Mt Moonlight Basin's water quality report?
As a community water system, Mt Moonlight Basin must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in Madison County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Big Sky County Water and Sewer Dist 363 | Madison | 4,132 | Community | Groundwater |
| Virginia City Water Dept | Madison | 1,500 | Community | Groundwater |
| Ennis Town of | Madison | 1,400 | Community | Groundwater |
| Sheridan Town of | Madison | 632 | Community | Groundwater |
| Nevada City | Madison | 621 | Transient non-community | Groundwater |
| Earthquake Lake Visitor Center | Madison | 503 | 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, “Mt Moonlight Basin, PWSID MT0004023, Montana”, https://aquacensus.com/water-systems/montana/mt-moonlight-basin-mt0004023 (data as of October 1, 2026).