Public water system · 010106001
ActiveMashantucket Pequot Water System
At a glance
Mashantucket Pequot Water System (PWSID 010106001) is an active community water system in Connecticut. It reports serving 22,171 people through 119 service connections. Its primary water source is groundwater under influence of surface water, and EPA lists it as Native American-owned. Of the 12 most recent violations in EPA's records, 2 are health-based, and the most recent began in July 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
22,171
Service connections
119
Primary source
GU
Groundwater under influence of surface water
System type
CWS
Community water system
System record
How does Mashantucket Pequot Water System compare with other water systems in Connecticut?
By EPA's size categories, Mashantucket Pequot Water System is a large system (10,001 to 100,000 people). Across Connecticut, the 2,363 active systems average 1,247 people each. Nationally, the average active community water system reports serving 6,703 people, so Mashantucket Pequot Water System is about 3.3 times 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. Connecticut has 481 active community water systems, 20% of the state's 2,363 active systems. Groundwater under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules. 3 Connecticut systems (0.1%) list groundwater under influence of surface water as their primary source.
Who owns and regulates Mashantucket Pequot Water System?
EPA lists Mashantucket Pequot Water System as Native American-owned. The EPA Region 01 is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act.
Does Mashantucket Pequot Water System have drinking water violations?
Of the 12 most recent violations in EPA's records, 2 are health-based, and the most recent began in July 2025. The violations listed here began between January 2016 and July 2025. By type: 5 monitoring and reporting, 4 public notice, recordkeeping or other, 2 contaminant level above the legal limit and 1 reporting. The contaminant or rule involved most often is Total trihalomethanes (TTHM) (4 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 |
|---|---|---|---|---|
| 2025-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Inadequate Reporting · code 72 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2024-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Inadequate Reporting · code 72 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2018-11-01 | ReportingReport Sample Result/Fail Monitor (RTCR) · code 4B | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2018-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2018-09-28 | Public notice, recordkeeping or otherPublic Notification Violation for NPDWR Violation · code 75 | Public Noticecode 7500 | No | Resolved |
| 2018-08-09 | Monitoring and reportingFailure Submit IDSE/Subpart V Plan Rpt · code 35 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2018-07-01 | Monitoring and reportingFailure Submit IDSE/Subpart V Plan Rpt · code 35 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2018-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Total trihalomethanes (TTHM)code 2950 | Yes | Resolved |
| 2018-04-02 | Public notice, recordkeeping or otherPublic Notification Violation for NPDWR Violation · code 75 | Public Noticecode 7500 | No | Archived |
| 2016-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Chlordanecode 2959 | No | Resolved |
| 2016-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Di(2-ethylhexyl) phthalatecode 2039 | No | Resolved |
| 2016-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Methoxychlorcode 2015 | 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.
Mashantucket Pequot Water System: frequently asked questions
Who runs Mashantucket Pequot Water System?
Mashantucket Pequot Water System (PWSID 010106001) is a community water system Native American-owned. It is regulated by the EPA Region 01.
How many people does Mashantucket Pequot Water System serve?
Mashantucket Pequot Water System reports serving 22,171 people through 119 service connections in Connecticut.
Where does Mashantucket Pequot Water System get its water?
EPA SDWIS lists this system's primary water source as groundwater under influence of surface water. Groundwater under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules.
Does Mashantucket Pequot Water System have any drinking water violations?
Of the 12 most recent violations in EPA's records, 2 are health-based, and the most recent began in July 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 Mashantucket Pequot 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, 2 are health-based, and the most recent began in July 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the EPA Region 01.
Where can I find Mashantucket Pequot Water System's water quality report?
As a community water system, Mashantucket Pequot 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 Connecticut
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Regional Water Authority | New Haven | 418,900 | Community | Surface water |
| Metropolitan District Commission | Hartford | 390,887 | Community | Surface water |
| Aquarion-Eastern Fairfield County | Fairfield | 351,756 | Community | Surface water |
| Aquarion-Stamford | Fairfield | 119,214 | Community | Surface water |
| Waterbury Water Department | New Haven | 107,271 | Community | Surface water |
| Ctwc - Northern Reg-Western System | Hartford | 101,313 | 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, “Mashantucket Pequot Water System, PWSID 010106001, Connecticut”, https://aquacensus.com/water-systems/connecticut/mashantucket-pequot-water-system-010106001 (data as of October 1, 2026).