Notice of Public Hearing and Comment Period on Water Quality Standards Rulemaking Before the Montana Department of Environmental Quality On April 24, 2026, the Montana Department of Environmental Quality (department) initiated rulemaking on rule amendments to update department Circular DEQ-7. Circular DEQ-7 contains numeric water quality standards for surface water and ground water and is incorporated by reference into the Administrative Rules of Montana. The department is proposing several amendments to Circular DEQ-7: Amend human health standard for cyanide in ground water to express cyanide as free cyanide rather than total cyanide, to add a required reporting value, and to add a nondegradation trigger value; Amend human health standards for lead in surface water and ground water, lowering the criteria from 15µg/L to 10 µg/L, and update the reference for the source used to derive the criteria; Amend human health standards for four pesticides (i.e., 1,2-dibromoethane, nicosulfuron, chlorsulfuron, and imazapic) to correct errors made when calculating their criteria prior to their adoption in 2017; and Amendments to correct grammatical errors, improve clarity, and remove outdated references. The department also proposes to amend 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. On June 8, 2026, at 11:00 a.m., a public hearing will be held in the Wilderness Room on the second floor at 2401 Colonial Drive, Helena, Montana, to consider rule amendments as proposed in MAR 2026-496.1 in the Montana Administrative Register. You may also join the hearing virtually via Zoom. More information is available on the department’s website, including a copy of the notice of public hearing on proposed amendments, and instructions on how to attend remotely, at https://deq.mt.gov/public/water-public. The department will make reasonable accommodation for persons with disabilities who wish to participate in this rulemaking process or need an alternative accessible format of this notice (see the MAR notice on the website for details). A copy of the proposed Circular DEQ-7 may be viewed at the department’s website using the following web address: https://deq.mt.gov/public/water-public; copies may also be obtained by contacting Katie Makarowski at (406) 444-3639 or kmkarowski@mt.gov. You are invited to submit data, views, or arguments concerning the proposed action either orally or in writing at the hearing. Written data, views, or arguments may also be submitted to the Department of Environmental Quality, P.O. Box 200901, Helena, Montana 59620-0901; or e-mailed to DEQMAR496@mt.gov and must be received no later than 5:00 p.m. on June 8, 2026. (12279422) 5/24, 5/31, 6/7. MNAXLP