Public water system · IL0150350
ActiveThomson
At a glance
Thomson (PWSID IL0150350) is an active community water system in Carroll County, Illinois. It reports serving 580 people through 237 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. EPA's records list 6 violations for this system; 1 is health-based, and the most recent began in July 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
580
Service connections
237
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Thomson compare with other water systems in Carroll County?
By EPA's size categories, Thomson is a small system (501 to 3,300 people). Carroll County has 35 active public water systems. Its population served is about 51% above the county average of 384 people per system, and accounts for 4.3% of the 13,444 people reported by systems filed under the county. Across Illinois, the 3,872 active systems average 3,204 people each. Nationally, the average active community water system reports serving 6,703 people, so Thomson 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. Illinois has 1,773 active community water systems, 46% of the state's 3,872 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 2,808 Illinois systems (73%) list groundwater as their primary source.
Who owns and regulates Thomson?
EPA lists Thomson as owned by a local government. The IL 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 35 active systems in Carroll County (23%) are also owned by a local government.
Does Thomson have drinking water violations?
EPA's records list 6 violations for this system; 1 is health-based, and the most recent began in July 2025. The violations listed here began between June 1977 and July 2025. By type: 4 monitoring and reporting, 1 reporting and 1 contaminant level above the legal limit. The contaminant or rule involved most often is Combined Radium (-226 and -228) (4 of them). EPA lists 4 as resolved, 1 as unaddressed 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. Unaddressed means the violation is not resolved or archived and is not yet covered by formal enforcement. 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 |
|---|---|---|---|---|
| 2025-07-02 | ReportingNotification, Known or Potential LSL · code 4H | Lead and Copper Rule Revisionscode 5200 | No | Unaddressed |
| 2022-07-01 | Monitoring and reportingMonitoring, Regular · code 03 | Combined Radium (-226 and -228)code 4010 | No | Resolved |
| 2021-10-01 | Monitoring and reportingMonitoring, Regular · code 03 | Combined Radium (-226 and -228)code 4010 | No | Resolved |
| 2015-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2002-10-01 | Monitoring and reportingMonitoring, Regular · code 03 | Combined Radium (-226 and -228)code 4010 | No | Resolved |
| 1977-06-30 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Archived |
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.
Thomson: frequently asked questions
Who runs Thomson?
Thomson (PWSID IL0150350) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Thomson serve?
Thomson reports serving 580 people through 237 service connections in Carroll County, Illinois.
Where does Thomson 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 Thomson have any drinking water violations?
EPA's records list 6 violations for this system; 1 is 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 Thomson'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 July 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the IL state drinking water program.
Where can I find Thomson's water quality report?
As a community water system, Thomson 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 Carroll County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Savanna | Carroll | 3,020 | Community | Groundwater |
| Thomson Maximum Security Center | Carroll | 2,166 | Community | Purchased groundwater |
| Lanark | Carroll | 1,504 | Community | Groundwater |
| Mount Carroll | Carroll | 1,479 | Community | Groundwater |
| Milledgeville | Carroll | 989 | Community | Groundwater |
| Shannon | Carroll | 801 | 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, “Thomson, PWSID IL0150350, Illinois”, https://aquacensus.com/water-systems/illinois/thomson-il0150350 (data as of October 1, 2026).