2026-10722RuleWallet

Montana Miners Can Now Define Their Own Damage Terms

Published Date: 5/29/2026

Rule

Summary

Montana’s mining rules just got an upgrade! Starting June 29, 2026, mining companies can now define “material damage” more clearly and even submit their own water impact info if the state or feds can’t provide it. This change helps miners and regulators work smarter, keeping Montana’s land and water safer without slowing down permits or adding big costs.

Analyzed Economic Effects

5 provisions identified: 3 benefits, 0 costs, 2 mixed.

New "Material Damage" Hydrology Definition

Montana adopted a new definition for "material damage" to the hydrologic balance that takes effect June 29, 2026. Material damage now means a quantifiable adverse impact on surface or groundwater that precludes an existing or reasonably foreseeable use, where "quantifiable adverse impact" must be measurable to a significant degree of confidence and uses are those classified under Montana law.

Alluvial Valley Floor Protection Defined

Montana now defines "material damage" to an alluvial valley floor as degradation or reduction of water quality or quantity that significantly decreases the valley floor's ability to support agricultural activities. This definition is part of the approved changes effective June 29, 2026.

Subsidence Material Damage Standard

Montana adopted a subsidence definition for "material damage" that covers functional impairment of lands, significant loss in production or income, or significant changes to a structure's condition, appearance, or utility. This definition matches the Federal subsidence standard and is effective June 29, 2026.

Operators May Use Self-Collected Hydrologic Data

Montana now allows a permit applicant to use hydrologic information they collected themselves to support the Probable Hydrologic Consequences (PHC) determination when an appropriate Federal or State agency does not have that information available. This change is approved and effective June 29, 2026.

No Retroactive Application; Effective Date Set

OSM approved Montana's amendment with an effective date of June 29, 2026, and determined that the parts of HB 587 attempting retroactive application to pending matters cannot be applied retroactively under SMCRA and federal rules. Parties with pending but undecided actions on or after the effective date cannot have these amendments applied retroactively.

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Key Dates

Published Date
Rule Effective
5/29/2026
6/29/2026

Department and Agencies

Department
Independent Agency
Agency
Interior Department
Surface Mining Reclamation and Enforcement Office
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