Water Quality | Department Circular DEQ-7 (Montana Numeric Water Quality Standards) Rulemaking | Comment Period Ends June 8, 2026 | Public Hearing June 8, 2026

April 24 2026

The notice of proposed rulemaking pertaining to department Circular DEQ-7 updates was published in Issue 8 of the Montana Administrative Register today (April 24, 2026) as Notice No. 2026-496.1.

The proposed rulemaking amends Circular DEQ-7 to a) update the human health water quality standard for cyanide in ground water to express cyanide as free cyanide rather than total cyanide, add a required reporting value, and add a nondegradation trigger value; b) update the human health water quality standards for lead in surface water and ground water and update the reference for the source used to derive the criteria; c) update the human health water quality standards for four pesticides (i.e., 1,2-dibromoethane, nicosulfuron, chlorsulfuron, and imazapic) to correct errors made in the previous calculation of their criteria; and d) correct grammatical errors, improve clarity of the Circular, and remove outdated references. The proposed rulemaking also amends ten rules to replace references to the 2019 edition of Circular DEQ-7 with references to the effective month and year of this rule amendment.

Associated materials and links:

How to submit public comments:

Mail comments to:
Department of Environmental Quality
Water Quality Planning Bureau
P.O. Box 200901
Helena, Montana 59620-0901

Or e-mail comments to: DEQMAR496@mt.gov

Comment period ends on June 8, 2026, at 5:00 p.m.

Public hearing information:

June 8, 2026, at 11:00 a.m.
Wilderness Room (second floor)
2401 Colonial Drive
Helena, MT 59601

Or, join the hearing online via Zoom:

https://mt-gov.zoom.us/j/83089983448?pwd=H6mhwvZx5yqywmYZybKNaHt6rFtWR4.1

Webinar ID: 830 8998 3448

Passcode: 047200

Telephone: (646) 558-8656

Tags: Public Comment, Water, Public Meeting and Rule Making