Protecting Public Health and the Environment.

Water Quality: Docket No. 58-0102-1803 - Final Rule

Rulemaking initiated to allow de minimis additions of heat in waters that exceed applicable temperature criteria.

Public Comment Opportunities | Negotiated Rulemaking History

Status of Rulemaking

Pending rule approved by the Idaho Legislature. Final and effective April 11, 2019. Final rule package submitted to EPA for approval April 15, 2019.

Final Rule Package Submitted to EPA

For more information, go to

This submittal also includes documents that exist as part of the rulemaking record and posted below.

Effective Date

April 11, 2019

2019 Legislative Rules Review

Pending rule approved by the Idaho Legislature.

November 2018 Board of Environmental Quality Meeting

Rulemaking Documents Required by Idaho Administrative Procedure Act


This rulemaking has been initiated to allow de minimis additions of heat when waters exceed applicable temperature criteria due to man-made causes. Currently, Idaho’s point source treatment requirements allow point sources of heat to raise receiving water temperatures up to 0.3°C only when the receiving water is naturally warmer than numeric criteria. There is not an allowance for any increase, however small, when it cannot be shown receiving water temperatures are naturally warmer than criteria.

Idaho has many very small point sources. All add some heat to the waters to which they discharge. And, in most cases, the water bodies to which they discharge are warmer than Idaho’s numeric temperature criteria set to protect aquatic life for a portion of each year. Heat is a non-conservative pollutant, and the sources of heat can be relatively small. This rulemaking proposes allowing NPDES/IPDES regulated human sources of heat loading to cause no more than a de minimis 0.3°C increase in receiving water temperatures. This would allow a 0.3°C increase to waters that are exceeding the numeric temperature criteria upstream for the designated aquatic life use even in cases where the exceedance of numeric criteria is not due to natural conditions.

Effective for Clean Water Act Purposes

Water quality standards adopted and submitted to EPA since May 30, 2000, are not effective for federal Clean Water Act (CWA) purposes until EPA approves them (see 40 CFR 131.21). This is known as the Alaska Rule. This rulemaking will be promulgated so that the existing rule, which continues to be effective for CWA purposes, remains in the Idaho Administrative Code until EPA approves the rule revisions. Notations explaining the effectiveness of the rule sections are also included. Upon EPA approval, the revised rule will become effective for CWA purposes and the previous rule and notations will be deleted from the Idaho Administrative Code. Information regarding the status of EPA review will be posted at here.

Public Comment Opportunities

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

Paula Wilson
Idaho Department of Environmental Quality
1410 N. Hilton, Boise, ID 83706
Fax: (208) 373-0481,

Comment Deadline

October 5, 2018

Written Public Comments on Proposed Rule

Submitted By Date Received
City of Nampa 10/04/18 
Idaho Conservation League (ICL) 10/05/18
U.S. EPA Region 10 10/11/18

Negotiated Rulemaking History

The text of the proposed rule was drafted based on discussions held and concerns raised during negotiations conducted pursuant to Idaho Code § 67-5220 and IDAPA The Notice of Negotiated Rulemaking was published in the July 2018 issue of the Idaho Administrative Bulletin, a preliminary draft rule was made available for public review on June 25, 2018, and a meeting was held on July 20, 2018. Key information was posted on the DEQ rulemaking web page and distributed to the public. Members of the public participated in the negotiated rulemaking process by attending the meetings and by submitting written comments.

All comments received during the negotiated rulemaking process were considered by DEQ when making decisions regarding development of the rule.  At the conclusion of the negotiated rulemaking process, DEQ formatted the final draft for publication as a proposed rule. The negotiated rulemaking record, which includes the negotiated rule drafts, written public comments, documents distributed during the negotiated rulemaking process, and the negotiated rulemaking summary, is available on this web page.

Negotiated Rulemaking Meeting Schedule

No additional meetings are scheduled.

Previous Meetings

July 20, 2018 - Agenda | Sign-in Sheets

Draft Negotiated Rule and Meeting Presentation Documents

Draft Negotiated Rule Date Posted Date of Meeting Discussion Written Comment Deadline
Draft No. 2


N/A DEQ is not requesting public comments on this draft. The next comment period will commence upon publication of the proposed rule in the September 5, 2018, issue of the Idaho Administrative Bulletin. The proposed rule comment deadline is October 5, 2018.

Preliminary Draft (Draft No. 1)

De Minimus Heat Additions - Discussion Paper #1

De Minimus Heat Additions  - DEQ PowerPoint Presentation









07/20/18 07/30/18

Written Public Comments

Comment Submitted By Date Received
Comment on Draft No. 1 Ron Harriman 07/20/18
Comment on Draft No. 1 Hubert Osborne 07/23/18
Comment on Draft No. 1 Idaho Conservation League (ICL) 07/30/18
Comment on Draft No. 1 City of Boise 07/30/18
Comment on Draft No. 1 Association of Idaho Cities (AIC) 07/30/18
Comment on Draft No. 1 City of Meridian 07/30/18
Comment on Draft No. 1 U.S. EPA Region 10 07/31/18

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Staff Contacts

Water Quality Standards Lead
DEQ State Office
Water Quality Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0502

Administrative Rules Coordinator
Paula Wilson
DEQ State Office
Attorney General's Office
1410 N. Hilton
Boise, ID 83706
(208) 373-0418