Somonauk STP
South Gage Street, Somonauk, IL 60552 · De Kalb County · Publicly Owned Treatment Works
- Average flow
- 0.15 MGD
- Design flow
- 0.75 MGD
- NPDES permit
- IL0020265
- Effective
- Permit expires
- March 2029
- Population served
- 1,424
- CWNS 2022
Somonauk STP is a publicly owned wastewater treatment works in Somonauk, De Kalb County, Illinois treating an average of 0.15 million gallons per day against a permitted design capacity of 0.75 MGD, serving about 1,424 residents. It discharges under NPDES permit IL0020265 (effective), which expires in March 2029, with 0 recorded violations in the last three years.
Treatment technology
3 treatment structures and unit processes identified at Somonauk STP.
Available with a free Klarifi account
See the full treatment train at Somonauk STP: structures, unit processes and planned upgrades, with exact unit counts.
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 Somonauk STP.
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Nearby wastewater treatment plants in Illinois
Sheridan · 7 mi away
0.32 MGD
Newark · 8 mi away
0.12 MGD
Plano · 8 mi away
0.76 MGD
Waterman · 10 mi away
0.25 MGD
Hinckley · 10 mi away
0.32 MGD
Big Rock · 11 mi away
0.03 MGD
Earlville · 12 mi away
0.34 MGD
Yorkville · 12 mi away
2.22 MGD
Somonauk 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 October 26, 2026; facility record last updated March 5, 2025.
Wastewater terms: POTW · MGD · NPDES permit · Inflow and infiltration · Tertiary treatment · Significant industrial user · all terms