Public water system · IL0990550
ActiveMendota
At a glance
Mendota (PWSID IL0990550) is an active community water system in LaSalle County, Illinois. It reports serving 7,100 people through 2,818 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, 9 are health-based, and the most recent began in July 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
7,100
Service connections
2,818
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Mendota compare with other water systems in LaSalle County?
By EPA's size categories, Mendota is a medium system (3,301 to 10,000 people). LaSalle County has 129 active public water systems, and Mendota is the 5th-largest of them by population served. Its population served is about 8.7 times the county average of 816 people per system, and accounts for 6.7% of the 105,319 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 Mendota is roughly in line with 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 Mendota?
EPA lists Mendota 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. 20 of the 129 active systems in LaSalle County (16%) are also owned by a local government.
Does Mendota have drinking water violations?
Of the 12 most recent violations in EPA's records, 9 are health-based, and the most recent began in July 2025. The violations listed here began between October 2006 and July 2025. By type: 9 contaminant level above the legal limit, 1 reporting, 1 public notice, recordkeeping or other and 1 monitoring and reporting. The contaminant or rule involved most often is Combined Radium (-226 and -228) (6 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 |
|---|---|---|---|---|
| 2025-07-02 | ReportingNotification, Known or Potential LSL · code 4H | Lead and Copper Rule Revisionscode 5200 | No | Resolved |
| 2025-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Inadequate Reporting · code 72 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2025-07-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2021-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Haloacetic acids (HAA5)code 2456 | Yes | Resolved |
| 2020-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Haloacetic acids (HAA5)code 2456 | Yes | Resolved |
| 2020-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Haloacetic acids (HAA5)code 2456 | Yes | Resolved |
| 2008-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2007-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2007-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2007-04-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2007-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2006-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | 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.
Mendota: frequently asked questions
Who runs Mendota?
Mendota (PWSID IL0990550) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Mendota serve?
Mendota reports serving 7,100 people through 2,818 service connections in LaSalle County, Illinois.
Where does Mendota 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 Mendota have any drinking water violations?
Of the 12 most recent violations in EPA's records, 9 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 Mendota'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, 9 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 IL state drinking water program.
Where can I find Mendota's water quality report?
As a community water system, Mendota 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 LaSalle County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Il American-Streator | LaSalle | 19,000 | Community | Surface water |
| Ottawa | LaSalle | 18,097 | Community | Groundwater |
| Peru | LaSalle | 10,300 | Community | Groundwater |
| La Salle | LaSalle | 9,700 | Community | Groundwater |
| Marseilles | LaSalle | 5,061 | Community | Groundwater |
| Prairie Path Water Company-Lake Holiday | LaSalle | 4,750 | 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, “Mendota, PWSID IL0990550, Illinois”, https://aquacensus.com/water-systems/illinois/mendota-il0990550 (data as of October 1, 2026).