Public water system · 083090050
ActiveAssiniboine & Sioux Rural Water System
At a glance
Assiniboine & Sioux Rural Water System (PWSID 083090050) is an active community water system in Montana. It reports serving 1,726 people through 245 service connections. Its primary water source is surface water, and EPA lists it as owned by the federal government. Of the 12 most recent violations in EPA's records, 7 are health-based, and the most recent began in April 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
1,726
Service connections
245
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Assiniboine & Sioux Rural Water System compare with other water systems in Montana?
By EPA's size categories, Assiniboine & Sioux Rural Water System is a small system (501 to 3,300 people). Across Montana, the 2,378 active systems average 489 people each. Nationally, the average active community water system reports serving 6,703 people, so Assiniboine & Sioux Rural Water System 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. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 60 Montana systems (2.5%) list surface water as their primary source.
Who owns and regulates Assiniboine & Sioux Rural Water System?
EPA lists Assiniboine & Sioux Rural Water System as owned by the federal government. The EPA Region 08 is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act.
Does Assiniboine & Sioux Rural Water System have drinking water violations?
Of the 12 most recent violations in EPA's records, 7 are health-based, and the most recent began in April 2025. The violations listed here began between June 2013 and April 2025. By type: 7 required treatment not met, 4 monitoring and reporting and 1 monitoring. The contaminant or rule involved most often is Carbon, total (5 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 |
|---|---|---|---|---|
| 2025-04-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2025-04-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2023-09-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2023-09-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2018-01-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2015-04-01 | Required treatment not metTreatment Technique Precursor Removal · code 46 | Carbon, totalcode 2920 | Yes | Resolved |
| 2015-01-01 | Required treatment not metTreatment Technique Precursor Removal · code 46 | Carbon, totalcode 2920 | Yes | Resolved |
| 2014-10-01 | Required treatment not metTreatment Technique Precursor Removal · code 46 | Carbon, totalcode 2920 | Yes | Resolved |
| 2014-07-01 | Required treatment not metTreatment Technique Precursor Removal · code 46 | Carbon, totalcode 2920 | Yes | Resolved |
| 2014-04-01 | Required treatment not metTreatment Technique Precursor Removal · code 46 | Carbon, totalcode 2920 | Yes | Resolved |
| 2013-06-01 | Required treatment not metMonthly Turbidity Exceed (Enhanced SWTR) · code 44 | Interim Enhanced Surface Water Treatment Rulecode 0300 | Yes | Resolved |
| 2013-06-01 | Required treatment not metSingle Turbidity Exceed (Enhanced SWTR) · code 43 | Interim Enhanced Surface Water Treatment Rulecode 0300 | 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.
Assiniboine & Sioux Rural Water System: frequently asked questions
Who runs Assiniboine & Sioux Rural Water System?
Assiniboine & Sioux Rural Water System (PWSID 083090050) is a community water system owned by the federal government. It is regulated by the EPA Region 08.
How many people does Assiniboine & Sioux Rural Water System serve?
Assiniboine & Sioux Rural Water System reports serving 1,726 people through 245 service connections in Montana.
Where does Assiniboine & Sioux Rural Water System get its water?
EPA SDWIS lists this system's primary water source as surface water. Surface water means the system draws its water from rivers, lakes, streams or reservoirs.
Does Assiniboine & Sioux Rural Water System have any drinking water violations?
Of the 12 most recent violations in EPA's records, 7 are health-based, and the most recent began in April 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 Assiniboine & Sioux Rural Water System'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, 7 are health-based, and the most recent began in April 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the EPA Region 08.
Where can I find Assiniboine & Sioux Rural Water System's water quality report?
As a community water system, Assiniboine & Sioux Rural Water System 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 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, “Assiniboine & Sioux Rural Water System, PWSID 083090050, Montana”, https://aquacensus.com/water-systems/montana/assiniboine-sioux-rural-water-system-083090050 (data as of October 1, 2026).