MSHA Proposes 18 Rules Reaffirming Underground MNM DPM Limit and Curtailing District Manager Authority in July 2025

MSHA issued 18 proposed rules that segment diesel particulate requirements by mine type and would limit district manager authority over training and certain plans. These proposals matter for audit planning across mixed surface and underground portfolios, but final text, effective dates, and transition mechanics remain uncertain.

Background

On July 1, 2025, MSHA proposed a package of 18 rules, including diesel particulate matter (DPM) provisions that distinguish between underground metal/nonmetal and underground coal operations, and restrictions on district manager (DM) authority over training programs and certain plan approvals (Jackson Lewis). Stakeholder comments on the proposals were due by July 31, 2025 (Jackson Lewis). The proposed training program restrictions apply to both surface and underground mines (Federal Register (2025-12231)).

Key Provisions

• DPM in underground metal/nonmetal: MSHA proposes reaffirming an exposure limit of 160 micrograms of total carbon per cubic meter of air (160 TC µg/m³) for underground metal/nonmetal mines (Jackson Lewis). This numerical limit remains the key benchmark for underground MNM DPM compliance under the proposal (Jackson Lewis).
• DPM in underground coal: MSHA proposes retaining an equipment emission limit of 2.5 grams per hour for diesel-powered equipment in underground coal mines (Jackson Lewis). The proposal explicitly distinguishes this coal standard from the underground MNM exposure limit (Jackson Lewis).
• Training programs: MSHA proposes eliminating district managers’ authority to require changes or additions to operator training programs beyond statutory criteria, and this proposal applies to both surface and underground mines (Federal Register (2025-12231)). This change targets approval authority rather than setting a new substantive training standard (Federal Register (2025-12231)).
• Roof control plans: MSHA proposes revising roof control plan regulations to remove district managers’ authority to impose additional measures in plan approvals (Regulations.gov (MSHA-2025-0072-0001)). This proposal addresses the scope of DM-imposed plan conditions (Regulations.gov (MSHA-2025-0072-0001)).
• Ventilation plan approvals: MSHA proposes revising ventilation plan approval criteria to eliminate district managers’ authority to require additional provisions (Regulations.gov (MSHA-2025-0084-0001)). Like the roof control proposal, this focuses on limiting approval add-ons rather than establishing a new numerical ventilation standard (Regulations.gov (MSHA-2025-0084-0001)).
• Rulemaking timing: The proposals were open for comment through July 31, 2025; final rule text, effective dates, and any phase-ins are not specified in the cited summaries (Jackson Lewis).

Decision Framework

Three threshold questions will drive near-term actions across mixed surface and underground portfolios: whether any sites are underground coal operations; which sites are underground MNM with diesel exposures; and where current training or plan approvals include DM-imposed add-ons. The answers determine which proposals trigger immediate operational alignment versus reliance on existing audit protocols pending final rules.

• If your portfolio includes underground MNM mines with diesel equipment, then the operative exposure benchmark in the proposal is 160 TC µg/m³, and inspection readiness should reflect that exposure-based standard (Jackson Lewis).
• If your portfolio includes underground coal mines, then the operative DPM benchmark in the proposal is an equipment emission limit of 2.5 grams per hour, which differs from the MNM exposure standard and warrants segmented compliance tracking by commodity (Jackson Lewis).
• If your sites operate under training programs subject to MSHA oversight, then the proposal to eliminate DM authority to require program changes applies to both surface and underground mines; the compliance impact will depend on how final rules address existing DM-imposed add-ons (Federal Register (2025-12231)).
• If your roof control or ventilation plan approvals contain DM-required provisions, then the proposals to curtail DM authority are material; whether operators can remove existing add-ons, or only avoid future add-ons, remains a transition question pending final text (Regulations.gov (MSHA-2025-0072-0001); Regulations.gov (MSHA-2025-0084-0001)).
• Before deciding, confirm: the presence or absence of underground coal sites; which underground MNM sites run diesel equipment; current DPM compliance baselines at those MNM sites; and where DM-imposed training or plan add-ons exist that could be affected if the proposals are finalized (citations above).

What We’re Monitoring

• Final rule text and effective/compliance dates for the DPM, training, roof control, and ventilation proposals; MSHA’s post-comment actions following the July 31, 2025 deadline (Jackson Lewis).
• Any MSHA explanation in final rules on how existing DM-imposed training or plan add-ons will be treated during transition (Federal Register (2025-12231); Regulations.gov (MSHA-2025-0072-0001); Regulations.gov (MSHA-2025-0084-0001)).
• Clarification of mine-type applicability for the roof control and ventilation plan proposals to refine surface vs. underground scoping (Regulations.gov (MSHA-2025-0072-0001); Regulations.gov (MSHA-2025-0084-0001)).