Public water system · IL1110650
ActiveMarengo
At a glance
Marengo (PWSID IL1110650) is an active community water system in McHenry County, Illinois. It reports serving 7,572 people through 2,810 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 October 2009.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
7,572
Service connections
2,810
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Marengo compare with other water systems in McHenry County?
By EPA's size categories, Marengo is a medium system (3,301 to 10,000 people). McHenry County has 192 active public water systems. Its population served is about 5.7 times the county average of 1,331 people per system, and accounts for 3% of the 255,516 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 Marengo is about 13% above 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 Marengo?
EPA lists Marengo 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. 35 of the 192 active systems in McHenry County (18%) are also owned by a local government.
Does Marengo have drinking water violations?
EPA's records list 6 violations for this system; 1 is health-based, and the most recent began in October 2009. The violations listed here began between June 1977 and October 2009. By type: 5 monitoring and reporting and 1 contaminant level above the legal limit. The contaminant or rule involved most often is Lead and Copper Rule (3 of them). EPA lists 3 as resolved and 3 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 |
|---|---|---|---|---|
| 2009-10-01 | Monitoring and reportingLead Consumer Notice · code 66 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2000-10-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Resolved |
| 1998-11-01 | Monitoring and reportingMonitoring, Routine Major (TCR) · code 23 | Total coliform bacteria (TCR)code 3100 | No | Archived |
| 1993-01-01 | Monitoring and reportingInitial Tap Sampling for Pb and Cu · code 51 | Lead and Copper Rulecode 5000 | No | Resolved |
| 1992-11-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Archived |
| 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.
Marengo: frequently asked questions
Who runs Marengo?
Marengo (PWSID IL1110650) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Marengo serve?
Marengo reports serving 7,572 people through 2,810 service connections in McHenry County, Illinois.
Where does Marengo 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 Marengo have any drinking water violations?
EPA's records list 6 violations for this system; 1 is health-based, and the most recent began in October 2009. 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 Marengo'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 October 2009. For current results, consult the system's annual water quality report, EPA ECHO, or the IL state drinking water program.
Where can I find Marengo's water quality report?
As a community water system, Marengo 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 McHenry County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Crystal Lake | McHenry | 40,661 | Community | Groundwater |
| Algonquin | McHenry | 30,700 | Community | Groundwater |
| Lake in the Hills | McHenry | 28,661 | Community | Groundwater |
| Huntley | McHenry | 28,495 | Community | Groundwater |
| Woodstock | McHenry | 25,630 | Community | Groundwater |
| Mchenry | McHenry | 22,335 | 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, “Marengo, PWSID IL1110650, Illinois”, https://aquacensus.com/water-systems/illinois/marengo-il1110650 (data as of October 1, 2026).