Monmouth Main STP
Monmouth, IL · Warren County · Publicly Owned Treatment Works
- Average flow
- —
- Design flow
- —
- NPDES permit
- ILL021253
- Effective
- Permit expires
- December 2030
- Population served
- —
- CWNS 2022
Monmouth Main STP is a publicly owned wastewater treatment works in Monmouth, Warren County, Illinois. Treatment on site includes clarifiers, uncovered lagoons. It discharges under NPDES permit ILL021253 (effective), which expires in December 2030, with 0 recorded violations in the last three years.
Treatment technology
Treatment structures identified at this facility. Exact unit counts are available in Klarifi.
Compliance snapshot (last 3 years)
- Total violations
- 0
- Effluent violations
- 0
Based on NPDES Discharge Monitoring Reports. Full violation history, parameters and discharge data available in the Klarifi platform.
Key contacts
Decision-makers at Monmouth Main STP.
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Nearby wastewater treatment plants in Illinois
Monmouth · 2 mi away
2.64 MGD
Kirkwood · 7 mi away
0.04 MGD
Alexis · 10 mi away
0.04 MGD
Galesburg · 11 mi away
3.22 MGD
Biggsville · 13 mi away
0.03 MGD
Abingdon · 16 mi away
0.27 MGD
Knoxville · 18 mi away
—
Stronghurst · 18 mi away
0.05 MGD
Monmouth Main STP: frequently asked questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed September 11, 2026; facility record last updated March 11, 2025.