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Community Water System · PWS IL1870150

Monmouth

Monmouth, Illinois 61462 - drinking water served from groundwater sources to 8,902 people, tracked in EPA SDWIS and UCMR5.

8,902
People served
269
EPA violations
208
Health-based
No PFAS
UCMR5 result

The verdict

EPA records 269 drinking-water violations at Monmouth, 77% of them health-based - above the Illinois per-system average.

269
Total EPA violations on record
77%
Health-based (MCL / treatment failure)
8,902
People served by this system
0
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Monmouth

Monmouth is a local-owned community water system that delivers drinking water to 8,902 residents in Monmouth, Illinois (Warren County) through 3,800 service connections. Its water is drawn from groundwater sources. EPA's Safe Drinking Water Information System records 269 total violations for this system , of which 208 (77%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 3 monitoring and reporting violations are on file. The most recent violation on record dates to 2024.

The most frequently cited contaminant at this system is Combined Radium (-226 and -228), recorded in 135 violations (MCL, health-based). This system was sampled under EPA's UCMR5 PFAS monitoring program and no PFAS compounds were detected above the minimum reporting level.

Across Illinois, EPA tracks 5,117 public water systems serving 12,576,876 people, with 355,322 cumulative violations and 52,932 health-based violations on record. About 81% of systems in the state carry at least one violation, and state-wide the average per system is 69.4 violations. Statewide, 199 of 487 UCMR5-tested systems have reported PFAS detections (40.9%).

Monmouth's 269 violations sit above the Illinois average.

All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

Population Served
8,902
Total Violations
269
Health-Based Violations
208
Water Source
Groundwater

System Details

System Type
Community
Owner Type
Local
Connections
3,800
County
Warren
School/Daycare
No
MCL Violations
208
Monitoring Violations
3
Treatment Tech Violations
0

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Combined Radium (-226 and -228) MCL 135 2024
Gross Alpha, Excl. Radon and U MCL 56 2005
Fluoride MCL 13 1983
Coliform (TCR) MCL 4 2001
Coliform (TCR) MR 2 1994
Public Notice Other 2 2024
Gross Alpha, Excl. Radon and U MR 1 1977

PFAS Testing Results (UCMR5)

Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 116 samples detected PFAS.

Contaminant Date Result MRL Status
4:2 FTS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFHxS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFMPA 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFHpS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFNA 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFOS 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFOA 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFDA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFDoA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFHxA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
8:2 FTS 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
PFPeS 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFBS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFUnA 7/31/2023 <2.00 ppt 2.00 ppt Not Detected
PFEESA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
NFDHA 7/31/2023 <20.00 ppt 20.00 ppt Not Detected
6:2 FTS 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
PFBA 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
HFPO-DA 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
ADONA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
9Cl-PF3ONS 7/31/2023 <2.00 ppt 2.00 ppt Not Detected
11Cl-PF3OUdS 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
PFMBA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFUnA 7/31/2023 <2.00 ppt 2.00 ppt Not Detected
PFOA 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
6:2 FTS 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
PFBA 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
HFPO-DA 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
11Cl-PF3OUdS 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
PFHxA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
4:2 FTS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFDA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
ADONA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFOS 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFNA 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFHxS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFBS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
9Cl-PF3ONS 7/31/2023 <2.00 ppt 2.00 ppt Not Detected
PFDoA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
8:2 FTS 7/31/2023 <5.00 ppt 5.00 ppt Not Detected
PFHpS 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeS 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFEESA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFMPA 7/31/2023 <4.00 ppt 4.00 ppt Not Detected
PFMBA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeA 7/31/2023 <3.00 ppt 3.00 ppt Not Detected
NFDHA 7/31/2023 <20.00 ppt 20.00 ppt Not Detected

Verify This Water System

The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Monmouth.

Federal Source of Truth

EPA SDWIS, Federal Reports

EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:

View PWS ID IL1870150 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

Illinois Drinking Water Authority

Illinois EPA, Bureau of Water is the primacy agency that licenses and inspects Monmouth under EPA-delegated authority.

Open IL regulator portal

Source: Illinois EPA, Bureau of Water

Violation Timeline

Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.

Year (latest) Contaminant Category Count EPA Record
2024 Combined Radium (-226 and -228) MCL 135 SDWIS / IL1870150 / 4010
2024 Public Notice Other 2 SDWIS / IL1870150 / 7500
2005 Gross Alpha, Excl. Radon and U MCL 56 SDWIS / IL1870150 / 4000
2001 Coliform (TCR) MCL 4 SDWIS / IL1870150 / 3100
1994 Coliform (TCR) MR 2 SDWIS / IL1870150 / 3100
1983 Fluoride MCL 13 SDWIS / IL1870150 / 1025
1977 Gross Alpha, Excl. Radon and U MR 1 SDWIS / IL1870150 / 4000

How Monmouth Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric Monmouth Illinois avg Federal benchmark
Total violations 269 69.4 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 208 10.3 Indicates a contaminant exceeded a federal MCL
PFAS detection None 40.9% EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 8,902 2,458 Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 5,117 regulated public water systems in Illinois.

Federal MCL reference, Safe Drinking Water Act thresholds ▼
Contaminant Federal MCL / Action Level Note
Lead 0 mg/L (Action Level: 0.015 mg/L) Lead and Copper Rule treatment technique
Arsenic 0.010 mg/L (10 ppb) Health-based MCL since 2006
Total Coliform Treatment technique (RTCR) Indicator organism, monitoring trigger
PFOA / PFOS (PFAS) 4.0 ppt each (final 2024 rule) Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026)
Nitrate (as N) 10 mg/L Acute health risk for infants

Frequently Asked Questions

Is Monmouth water safe to drink? ▼
Monmouth (PWS ID: IL1870150) has 269 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 8,902 people using Groundwater sources.
How many people does Monmouth serve? ▼
Monmouth serves 8,902 people in Monmouth, Illinois. It is a Local-owned system using Groundwater water sources with 3,800 service connections.
What type of violations does Monmouth have? ▼
Monmouth has 269 total violations: 208 health-based violations (MCL exceedances or treatment failures), 3 monitoring/reporting violations, and 0 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Monmouth water? ▼
No. Monmouth was tested for PFAS under the EPA's UCMR5 monitoring program and no PFAS contamination was detected.
What water source does Monmouth use? ▼
Monmouth uses Groundwater as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.
Where does this data come from? ▼
All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. PFAS data from EPA UCMR5 monitoring program (2023-2025). This data is provided for informational purposes only.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.