Stormwater Discharges from Municipal Sources in Idaho and Washington
Proposed permit for University of Idaho MS4 - Public comment period closes January 25, 2021.
Questions?
For questions about MS4 permits in Region 10, contact Misha Vakoc (vakoc.misha@epa.gov), 206-553-6650.
Join our mailing list: Contact Misha Vakoc to receive notification when the draft MS4 permits are available for review and comment.
General Information
Under the National Pollutant Discharge Elimination System (NPDES) stormwater program, operators of large, medium and regulated small municipal separate storm sewer systems (MS4s) require authorization to discharge pollutants under an NPDES permit.
In Region 10, EPA is the NPDES stormwater permitting authority for:
- Facilities in Idaho.
- Facilities on Indian Country lands in Oregon and Washington.
- Federal operators in Washington.
If your facility is not within one of the categories listed above, contact your state's municipal stormwater program:
- Alaska MS4 ProgramExit
- Oregon Municipal Stormwater PermitsExit
- Washington Stormwater General PermitsExit
- NPDES Stormwater Program in Region 10
- Stormwater Discharges from Municipal Sources
- NPDES Stormwater Final MS4 General Permit Remand Rule
MS4 Permits in Idaho
The EPA approved Idaho's application to administer and enforce the Idaho Pollutant Discharge Elimination System (IPDES) program. Under EPA’s approval, authority to issue stormwater permits will transfer to the Idaho Department of Environmental Quality in July 2021.
Visit Idaho NPDES Program Authorization to learn more about EPA's approval.
Which Idaho MS4s are regulated?
All MS4s in U.S. Census-defined Urbanized Areas of Idaho are regulated under the NPDES program (refer to the maps in the table below). See Individual MS4 Permits in Idaho for MS4 operators that have previously obtained individual MS4 permits from EPA.
| Census Urbanized Area (UA) Map | Regulated MS4 Operator |
|---|---|
| Boise City UA (PDF) (1 pg, 2.5MB)Exit | Ada County Highway District, Boise State University, Ada County Drainage District #3, City of Boise, City of Garden City, Idaho Transportation Dept. District #3 |
| Coeur d'Alene UA (PDF) (1 pg, 972K)Exit | Lakes Highway District, Post Falls Highway District, City of Coeur d'Alene, City of Post Falls, Idaho Transportation Dept. District #1 |
| Idaho Falls UA (PDF) (1 pg, 735K)Exit | City of Idaho Falls, Idaho Transportation Dept. District #6 |
| Lewiston UA (PDF) (1 pg, 446K)Exit | City of Lewiston, Idaho Transportation Dept. District #2 |
| Nampa UA (PDF) (1 pg, 1.3MB)Exit | Canyon Highway District #4, Nampa Highway District #1, City of Caldwell, City of Middleton |
| Pocatello UA (PDF) (1 pg, 640K)Exit | Bannock County, City of Chubbuck, City of Pocatello, Idaho Transportation Dept. District #5, Idaho State University |
Individual MS4 Permits in Idaho
See the table below for MS4 permits currently issued or under development.
| Facility or Permit Name | Permit Number | Effective Date | Expiration Date |
|---|---|---|---|
| Ada County Highway District MS4 | IDS028185 | 2021-02-01 | 2026-01-31 |
| Boise/Garden City Area MS4s (Ada County, Boise State University, City of Boise, City of Garden City, Drainage District #3, Idaho Transportation Dept. District #3) | IDS027561 | 2012-02-01 | 2018-01-30 |
| Idaho Transportation Dept. District #3 MS4 | IDS028177 | 2021-02-01 | 2026-01-31 |
| Caldwell MS4 | IDS028118 | 2020-12-01 | 2025-09-30 |
| Coeur d'Alene MS4 | IDS028215 | 2020-12-01 | 2025-09-30 |
| East Side Highway District MS4 (see North Idaho Highway Districts MS4s) | IDS028207 | 2020-10-01 | 2025-09-30 |
| Idaho Transportation Dept. District 1 MS4 | IDS028223 | 2020-12-01 | 2025-09-30 |
| Lakes Highway District MS4 (see North Idaho Highway Districts MS4s) | IDS028207 | 2020-10-01 | 2025-09-30 |
| Idaho Falls and Idaho Transportation Dept. District #6 MS4s | IDS028070 | 2020-10-01 | 2020-09-30 |
| Middleton MS4 | IDS028100 | 2020-10-01 | 2025-09-30 |
| Canyon Highway District No. 4 MS4 | IDS028134 | 2021-02-01 | 2026-01-31 |
| Nampa Highway District #1 MS4 | IDS028142 | 2009-10-15 | 2014-10-14 |
| Nampa MS4 | IDS028126 | 2021-02-01 | 2026-01-31 |
| Notus-Parma Highway District #2 MS4 | IDS028151 | 2009-10-15 | 2014-10-14 |
| Pocatello Urbanized Area MS4s (Pocatello, Chubbuck, Bannock County, Idaho Transportation Dept. District #5, and Idaho State University) | IDS028053 | 2019-10-01 | 2024-09-30 |
| Post Falls MS4 | IDS028231 | 2020-11-01 | 2025-09-30 |
| Post Falls Highway District MS4 (see North Idaho Highway Districts MS4s) | IDS028207 | 2020-10-01 | 2025-09-30 |
| City of Moscow MS4 | IDS028398 | 2019-10-01 | 2024-09-30 |
| City of Lewiston and Lewis-Clark State College MS4s | IDS028061 | 2020-11-01 | 2025-09-30 |
| Idaho Transportation Dept. District #2 MS4 | IDS028258 | 2020-11-01 | 2025-09-30 |
| University of Idaho MS4 | IDS028576 | N/A | N/A |
MS4 Permits in Washington
EPA Region 10 is the NPDES permitting authority for MS4 discharges operated by federal entities in Washington, regulated MS4s located in Indian Country, and/or regulated MS4s discharging to waters subject to tribal water quality standards.
If your facility is not within one of these categories, visit Washington Stormwater General PermitsExit for permitting information.
| Facility or Permit Name | Permit Number | Effective Date | Expiration Date |
|---|---|---|---|
| Naval Station Everett MS4 | WAS026640 | 02-01-2020 | 01-31-2026 |
| Naval Base Kitsap MS4 | WAS026646 | 02-01-2020 | 01-31-2026 |
| Naval Air Station Whidbey Island MS4 | WAS02661 | 02-01-2020 | 01-31-2026 |
| City of Tacoma MS4 Discharges to Puyallup Tribal Waters | WAS026680 | N/A | N/A |
| Pierce County MS4 Discharges to Puyallup Tribal Waters | WAS026875 | N/A | N/A |
| Washington State Department of Transportation MS4 Discharges to Puyallup Tribal Waters | WAS026743 | N/A | N/A |
| Tulalip Tribes MS4 | WAS026654 | N/A | N/A |