NPDES permits in Illinois
641 permits held by publicly owned wastewater treatment plants · issued by IEPA
Effective
621
Administratively continued
18
Expired
1
Total tracked
641
Illinois Environmental Protection Agency (IEPA) runs the NPDES program in Illinois under delegation from EPA Region 5, issuing and enforcing the discharge permits listed here. Klarifi tracks 641 permits held by publicly owned treatment plants in the state, with status, expiry, design flow and three-year compliance for each. Agency website →
An NPDES permit runs for five years. To keep discharging, a plant must apply for renewal at least 180 days before the expiry date, and the renewed permit usually arrives with tighter effluent limits, new monitoring requirements or a compliance schedule. That is why the year a permit expires is the year a plant starts budgeting for upgrades: nutrient removal, disinfection, capacity or controls.
Permit renewals by year
2029: 76 permits
2030: 144 permits
2031: 37 permits
Largest permit holders in Illinois
| Facility | City | Avg flow (MGD) | Design (MGD) | NPDES permit | Status | Expires | Violations (3y) |
|---|---|---|---|---|---|---|---|
| MWRDGC Terrence J O'Brien Water Reclamation Plant | Skokie | 170 | 450 | IL0028088 | Administratively continued | Jul 2022 | 18 |
| East Moline Wastewater | East Moline | 3.74 | 27.8 | IL0028550 | Effective | Mar 2031 | 2 |
| Sanitary District Of Decatur | Decatur | 26.53 | — | ILL028321 | Effective | Dec 2030 | 1 |
| Springbrook Water Reclamation Center | Naperville | 17.26 | — | ILL034061 | Effective | Dec 2030 | 0 |
| O Fallon STP | O Fallon | 1.98 | 14.6 | IL0021636 | Effective | Mar 2031 | 0 |
| Swansea Stp, Village Of | Swansea | 1 | 11.89 | IL0021181 | Effective | Mar 2031 | 5 |
| Bloomington Normal WRD -West STP | Bloomington | 10.71 | — | ILL027731 | Effective | Dec 2030 | 0 |
| Staunton Stp, City Of | Staunton | 0.21 | 10.7 | IL0031232 | Effective | Oct 2029 | 23 |
| Fox River Water Reclamation Dist | Elgin | 10 | — | ILL028657 | Effective | Dec 2030 | 51 |
| Sterling WWTP | Sterling | 4.31 | 9 | IL0060569 | Administratively continued | Sep 2024 | 5 |
| Flagg Creek Water Reclamation | Burr Ridge | 8.31 | — | ILL022586 | Effective | Dec 2030 | 5 |
| Itasca, Village Of - Prospect Avenue WWTP | Itasca | 0.9 | 8.2 | IL0079073 | Effective | Dec 2026 | 5 |
| Elmhurst Stp, City Of | Elmhurst | 7.92 | — | ILL028746 | Effective | Dec 2030 | 8 |
| Lake County Public Works Department | Buffalo Grove | 7.89 | — | ILL022055 | Effective | Dec 2030 | 1 |
| Spring Creek STP | Springfield | 7.59 | — | ILL021989 | Effective | Dec 2030 | 28 |
| Glenbard Wastewater Authority | Glen Ellyn | 7.04 | — | ILL021547 | Effective | Dec 2030 | 27 |
| Joliet West Stp, City Of | Joliet | 6.67 | — | ILL033553 | Effective | Dec 2030 | 0 |
| Downers Grove Sanitary District | Downers Grove | 6.39 | — | ILL028380 | Effective | Dec 2030 | 5 |
| Washington STP #2 | Washington | 1.13 | 6.37 | IL0042412 | Effective | Oct 2030 | 0 |
| Urbana & Champaign Sd | Urbana | 6.2 | — | ILL031500 | Effective | Dec 2030 | 2 |
| Christian County Water Reclamation District | Taylorville | 1.58 | 6.13 | IL0031356 | Effective | Jul 2031 | 0 |
| Woodridge-Greene Valley WWTP | Woodridge | 6.1 | — | ILL031844 | Effective | Dec 2030 | 2 |
| Duquoin Stp, City Of | Du Quoin | 0.42 | 6 | IL0028517 | Effective | Jul 2031 | 8 |
| Marengo Stp, City Of | Marengo | 0.24 | 5.94 | IL0020729 | Administratively continued | May 2026 | 46 |
| Alton Waste Water Treatment Plant | Alton | 5.38 | — | ILL027464 | Effective | Dec 2030 | 39 |
NPDES permits in Illinois: 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.