Protecting Public Health and the Environment.

Triennial Review

Section 303 of the Clean Water Act (CWA) requires states to modify and improve water quality standards (WQS) at least once every three years. Under this triennial review process, states review, modify, and adopt applicable WQS, taking into consideration public concerns, EPA guidance, and new scientific and technical information.

DEQ will accomplish five objectives as part of the 2020 Triennial Review process:

  1. Draft WQS issue papers
  2. Hold a public meeting to provide opportunity for public participation
  3. Release a draft Triennial Review Report
  4. Open a public comment period
  5. Submit the final report to EPA

The triennial review process is meant to identify issues. No changes to WQS will occur as part of the review.

Public Meeting

To comply with the CWA, DEQ will hold a public meeting to engage stakeholders and identify priorities for WQS rulemaking and sub-program development for the next three-plus years.

The public meeting is scheduled for May 19, 2020, from 6 to 9 p.m. MDT.

Meetings will be held remotely to comply with Governor Little's proclamation. Contact Michelle Dale for telephone and web conferencing information.

Public Participation

Interested parties are encouraged to attend. Written public comment opportunities will also be made available throughout the review process. Contact Michelle Dale with any questions or to sign up for email notifications.

Public Comment Opportunities

Submit all written comments by mail, fax or email to Michelle Dale:

Michelle Dale
Idaho Department of Environmental Quality
1410 N. Hilton, Boise, ID 83706
Fax: (208) 373-0576



Date of Meeting Discussion

Written Comment Deadline

2020 Triennial Review - DEQ PowerPoint Presentation

May 19, 2020 June 30, 2020 

Issue Paper: EPA §304(a) Recommended Criteria—Microcystins and Cylindrospermopsin

May 19, 2020 June 30, 2020 

Issue Paper: Comparison of Current Idaho Aquatic Life Criteria for Ammonia and EPA’s §304(a) Recommended Criteria

 May 19, 2020  June 30, 2020 

Issue Paper: Salmonid Spawning Use Designation

May 19, 2020  June 30, 2020  

Issue Paper: Data and Information Needs Necessary for the State of Idaho to Consider Adoption of EPA 304(a) Aquatic Life Criteria for Mercury

 May 19, 2020 June 30, 2020  

Issue Paper: Lower Snake – Asotin Subbasin (HUC 17060101) Salmonid Spawning Use Designation

 May 19, 2020 June 30, 2020  

Issue Paper: Jacks Creek Aquatic Life Beneficial Use Designation

May 19, 2020  June 30, 2020  

Issue Paper: Performance-based Approach for Temperature Criteria

May 19, 2020   June 30, 2020 
Workshop Presentation
2020 Triennial Review of Idaho Water Quality Standards
May 19, 2020  June 30, 2020  


Written Public Comments

Submitted By  Date Received 
Ronald Harriman (private citizen) 5/20/2020

Idaho Conservation League (ICL)

ICL comment revision re Idaho DEQ Triennial Review Mercury



Idaho Power Company (IPC) Triennial Review Aquatic Life Criteria for Mercury

Idaho Power Company (IPC) Triennial Review Asotin

Subbasin Idaho Power Company (IPC) Triennial Review SSC Temperature


Association of Idaho Cities (AIC)


Idaho Department of Fish and Game (IDFG)


Idaho Water Users Association (IWUA)


Nez Perce Tribe


Treasure Valley Water Users Association (TVWUA)


Upper Snake River Tribes Foundation (USRTF) Performance-Based Standards

Upper Snake River Tribes Foundation (USRTF) Salmonid Spawning


National Marine Fisheries Service (NMFS)



Public Comment Period on 2017 DRAFT Triennial Review of Idaho Water Quality Standards - Written Comment Deadline October 16, 2017


Date Posted

Written Comment Deadline

2017 Draft Triennial Review of Idaho Water Quality Standards September 14, 2017 October 16, 2017

Written Public Comments

Submitted by Date Received
Potlatch Corporation 09/21/17
U.S. National Oceanic and Atmospheric Administration (NOAA) 10/16/17

Public Comment Period on Water Quality Standards Triennial Review Documents and Workshop Presentation – Written Comment Deadline June 30, 2017

Water Quality Standards Triennial Review Issue Papers and Workshop Presentation

Written Comment Deadline

Issue Paper # 1
Modified Aquatic Life Use for Undesignated Waters
June 30, 2017

Issue Paper #2
Salmonid Spawning Use Designation

Issue Paper #3
Recreational Use and Criteria
Issue Paper #4
Comparison of Idaho Aquatic Life Criteria for Certain Toxic Substances with Current EPA § 304(a) Recommended Criteria – Acrolein, Ammonia, Cadmium, Carbaryl, Diazinon, and Selenium
Issue Paper #5
Cold Water Aquatic Life Criteria for Turbidity
Issue Paper #6
EPA Review and Approval of State Water Quality Standards (“Alaska Rule”)

Workshop Presentation
2017 Triennial Review of Idaho Water Quality Standards

Written Public Comments

Submitted by Date Received
Idaho Conservation League (ICL) 06/26/17
Potlatch 06/26/17
Hancock Forest Management 06/29/17
Idaho Department of Lands (IDL) 06/30/17
City of Nampa 06/30/17
City of Moscow 06/30/17
Idaho Water Users Association (IWUA) 06/30/17
City of Boise 06/30/17
U.S. EPA Region 10 06/30/17
Association of Idaho Cities (AIC) 07/05/17

Federal Mandate

The CWA requires states to adopt EPA’s recommended criteria, or develop their own, and routinely review and update water quality standards to ensure consistency with the requirements of the Act. Specifically, §303(c)(1) states the "...State shall from time to time (but at least once each three year period...) hold public hearings for the purpose of reviewing applicable water quality standards and, as appropriate, modifying and adopting standards." This public review period is referred to as the "triennial review."

In addition to requiring states to "open the book" to the public for their comments on state water quality standards, the CWA requires states to respond to EPA guidance on new toxic criteria as well. "Whenever a State reviews water quality standards... or revises or adopts new standards..., such State shall adopt criteria for all toxic pollutants listed pursuant to §307(a)(1) of this title for which criteria have been published under Section 304(a) of this title, the discharge or presence of which in the affected waters could reasonably be expected to interfere with those designated uses adopted by the State, as necessary to support such designated uses.” [§303(c)(2)(B)]

States are also required to identify those water bodies that are not designated or protected for fishable/swimmable uses and to determine if any new information has become available that will allow the attainment of these uses. If the state determines that the fishable/swimmable uses are, in fact, attainable in those water bodies, the WQS are to be revised accordingly. Similarly, the state should work to designate uses to water bodies that have not yet been designated in the WQS.

The CWA is emphatic about providing opportunities for public input and indicates that "public participation in the development, revision, and enforcement of any regulation, standard, effluent limitation, plan, or program established by... any State under this Act shall be provided for, encouraged and assisted by the... States." [§101(e)] "The State shall hold a public hearing for the purpose of reviewing water quality standards, in accordance with State law, EPA's water quality management regulations (40 CFR 130.3(b)(6)) and public participation regulation (40 CFR Part 25)." [40 CFR 131.20(b)]

Triennial Review Process 2014-16

The triennial review process is not a one-time exercise; rather it occurs in part whenever DEQ updates the water quality standards. The process outlined here may change as necessary in accordance with Idaho and federal rules in future triennial review cycles. Having processes in place is critical for managing workloads and producing results in a timely manner. The following information outlines the requirements of the CWA for reviewing water quality standards and sets forth the process by which DEQ intends to conduct its triennial review in 2014-16.

Development of Rulemaking Packages: 2015 - 2016

The triennial review process is intended to identify and prioritize needed changes to the WQS. DEQ intends to initiate rulemaking to make needed changes in accordance with its priorities and as agency resources allow. Issues for rulemaking set by the triennial review process, however, may change in subsequent years as a result of new information, litigation, legislative actions or other events. Access current DEQ rulemaking activities here.

Report to EPA: Completed November 2014

DEQ has compiled a report of all of the triennial review findings and submitted it to EPA in November 2014.

Supporting Documents

Issue Papers

Public Workshops and Public Comment Period: Completed June - August 2014

Three public workshops directed by DEQ staff were held at DEQ’s State Office in Boise to discuss the Potential Triennial Review Items proposed for review and receive input on additional WQS topics which may need consideration according to the public. Issue papers were also made available for public review and discussion at the workshops. The public workshops were broadcast via teleconference to DEQ's regional offices so that participation was not limited to only those who could attend the Boise workshop location. The first workshop was held June 25, the second July 30, and the third August 20. The workshops were informal and designed to present or clarify the information posted on DEQ’s website and to receive feedback from the public on their WQS interests and concerns.

DEQ allowed for a public comment period following each workshop for members of the public to submit comments on the information presented during that specific workshop. DEQ will post on its website any comments received from the public.

Workshop Materials

Workshop 1: June 25, 2014

Workshop 2: July 30, 2014

Workshop 3: August 20, 2014

Public Announcement: Completed May 2014

In May 2014, issued a DEQ public announcement of planned public workshops and provided a list of Potential Triennial Review Items for the current triennial review for public review. The public was invited to review the list and attend the workshops to discuss these and any other topics that the public believes should be addressed.

Planning: Completed February - April 2014

A work group consisting of individuals within the agency who have direct knowledge and experience working with the WQS, and who will be otherwise involved in the triennial review proceedings, was assembled. The work group formulated a list of issues pertaining to the standards which need to be reviewed and/or revised. This list was shared with regional staff for additional input and priorities assessment. The agency then prepared a priorities list and publicly announced the list along with a schedule of public workshops.

Agency staff prepared issue summaries for each of the proposed standards on the list to be considered for review or revision during the current triennial review process. These summaries present the public with important information pertaining to the particular standards. It should be made clear to the public that not all of the potential items in need of review and updating will be tackled at once. The agency also has to consider workload, resources and priorities over the ensuing triennial review period.