Who issues NPDES permits in Idaho?

Idaho Department of Environmental Quality issues and enforces NPDES permits for wastewater discharges in Idaho. Klarifi tracks 94 permits held by publicly owned treatment plants in the state.

How many NPDES permits in Idaho are expired or administratively continued?

77 permits are administratively continued (the plant applied for renewal and the old permit stays in force) and 1 are recorded as expired, out of 94 permits tracked. 16 are effective.

How many Idaho wastewater permits come up for renewal soon?

6 in 2026, 4 in 2027 and 7 in 2028. Each year has its own renewal calendar with the plants listed.

How do I look up an NPDES permit number?

Enter the permit number (two letters and seven characters, for example TX0021873) or the plant name in the lookup on the NPDES page; each result opens the plant profile with status, expiry, design flow and the three-year violation count.

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NPDES permits in Idaho

Name: NPDES permits held by wastewater treatment plants in Idaho
Creator: Klarifi
License: https://klarifi.io/terms-of-service

94 permits held by publicly owned wastewater treatment plants · issued by IDEQ

Effective

Administratively continued

Expired

Total tracked

Idaho Department of Environmental Quality (IDEQ) runs the NPDES program in Idaho under delegation from EPA Region 10, issuing and enforcing the discharge permits listed here. Klarifi tracks 94 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

2026: 6 permits →

2027: 4 permits

2028: 7 permits →

2029: 1 permits

2030: 1 permits

2031: 1 permits

Largest permit holders in Idaho

The 25 largest publicly owned wastewater treatment plants in Idaho by permitted design flow, with NPDES permit number, status and expiry. Source: EPA ICIS-NPDES via Klarifi.
Facility	City	Avg flow (MGD)	Design (MGD)	NPDES permit	Status	Expires	Violations (3y)
West Boise WWTP	Garden City	62	24	ID0023981	Effective	Jun 2027	9
Pocatello City WWTP	Pocatello	6.79	12	ID0021784	Administratively continued	Aug 2017	8
Nampa WWTP	Nampa	—	11.76	ID0022063	Administratively continued	Oct 2021	27
Rexburg WWTP	Rexburg	—	6	ID0023817	Effective	Mar 2028	41
Emmett WWTP	Emmett	1.76	5.7	ID0020311	Administratively continued	Jan 2007	2
Lewiston WWTP	Lewiston	3.31	5.7	ID0022055	Administratively continued	Jan 2021	0
Page WWTP	Smelterville	1.36	4.3	ID0021300	Administratively continued	Sep 2018	1
Ketchum Sun Valley WWTP	Ketchum	1.02	4	ID0020281	Administratively continued	Jul 2017	0
Moscow STP	Moscow	0.85	4	ID0021491	Effective	Jan 2031	0
Kuna North WWTP	Meridian	1.23	3.5	ID0028355	Administratively continued	May 2014	5
Jerome WWTP	Jerome	3.59	3	ID0020168	Administratively continued	Jun 2015	4
Payette WWTP	Payette	1	2.88	ID0020672	Administratively continued	Oct 2019	1
Mccall WWTP	Mccall	—	2.65	ID0020231	Administratively continued	Apr 2008	0
Hayden Area Regional Sewer Board WWTP	Hayden	—	2.4	ID0026590	Effective	May 2029	5
Weiser WWTP	Weiser	—	2.4	ID0020290	Administratively continued	Dec 2016	0
Oxbow WWTP	Shelley	1.93	2	ID0020133	Administratively continued	May 2019	0
St Maries WWTP	Saint Maries	—	2	ID0022799	Expired	Oct 2025	36
Star WWTP	Star	1.58	1.85	ID0023591	Administratively continued	Apr 2020	0
Soda Springs WWTP	Soda Springs	0.86	1.7	ID0020818	Administratively continued	Jun 2025	1
American Falls WWTP	American Falls	0.53	0.9	ID0020753	Administratively continued	Jul 2019	2
Grangeville WWTP	Grangeville	0.39	0.88	ID0020036	Administratively continued	Apr 2025	3
Firth WWTP	Firth	0.05	0.8	ID0024988	Administratively continued	Mar 2018	0
St Anthony Sewage Lagoon	Saint Anthony	0.26	0.8	ID0020401	Administratively continued	Nov 2014	7
Parma WWTP	Parma	0.11	0.68	ID0021776	Administratively continued	Mar 2022	82
Buhl WWTP	Buhl	0.29	0.67	ID0020664	Administratively continued	Oct 2012	2

All 94 plants in Idaho →

NPDES permits in Idaho: 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.

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