Public water system · 083090040
ActiveIsland Mountain Development Group
At a glance
Island Mountain Development Group (PWSID 083090040) is an active non-transient non-community water system in Montana. It reports serving 150 people through 1 service connection. Its primary water source is groundwater, and EPA lists it as Native American-owned. EPA's records list 6 violations for this system; 1 is health-based, and the most recent began in November 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
150
Service connections
1
Primary source
GW
Groundwater
System type
NTNCWS
Non-transient non-community water system
System record
How does Island Mountain Development Group compare with other water systems in Montana?
By EPA's size categories, Island Mountain Development Group is a very small system (500 people or fewer). Across Montana, the 2,378 active systems average 489 people each. Nationally, the average active non-transient non-community water system reports serving 430 people, so Island Mountain Development Group is about 65% below that figure.
What does “non-transient non-community water system” mean?
A non-transient non-community water system regularly serves at least 25 of the same people for more than six months a year, but not where they live. Schools, factories, office buildings and hospitals with their own supply are typical examples. Montana has 319 active non-transient non-community water systems, 13% 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 Island Mountain Development Group?
EPA lists Island Mountain Development Group 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 Island Mountain Development Group have drinking water violations?
EPA's records list 6 violations for this system; 1 is health-based, and the most recent began in November 2025. The violations listed here began between February 2019 and November 2025. By type: 4 monitoring and reporting, 1 required treatment not met and 1 monitoring. The contaminants or rules involved are E. coli, Long Term 2 Enhanced Surface Water Treatment Rule, Nitrate-Nitrite and Lead and Copper Rule. EPA lists 6 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 |
|---|---|---|---|---|
| 2025-11-28 | Monitoring and reportingMonitoring, Source Water (GWR) · code 34 | E. colicode 3014 | No | Resolved |
| 2023-09-07 | Required treatment not metFailure To Address Deficiency · code 45 | Long Term 2 Enhanced Surface Water Treatment Rulecode 0800 | Yes | Resolved |
| 2023-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Nitrate-Nitritecode 1038 | No | Resolved |
| 2021-12-30 | Monitoring and reportingLead Consumer Notice · code 66 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2020-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Endothallcode 2033 | No | Resolved |
| 2019-02-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
All 6 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.
Island Mountain Development Group: frequently asked questions
Who runs Island Mountain Development Group?
Island Mountain Development Group (PWSID 083090040) is a non-transient non-community water system Native American-owned. It is regulated by the EPA Region 08.
How many people does Island Mountain Development Group serve?
Island Mountain Development Group reports serving 150 people through 1 service connection in Montana.
Where does Island Mountain Development Group 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 Island Mountain Development Group have any drinking water violations?
EPA's records list 6 violations for this system; 1 is health-based, and the most recent began in November 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 Island Mountain Development Group'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 6 violations for this system; 1 is health-based, and the most recent began in November 2025. For current results, consult EPA ECHO, or the EPA Region 08.
Where can I find Island Mountain Development Group's water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. Island Mountain Development Group is a non-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, “Island Mountain Development Group, PWSID 083090040, Montana”, https://aquacensus.com/water-systems/montana/island-mountain-development-group-083090040 (data as of October 1, 2026).