MSHA Proposes 18-Rule Package Reaffirming Underground DPM Limits and Curtailing District Manager Authority (July 1, 2025)

Executive Summary

MSHA proposed 18 rules on July 1, 2025, including reaffirmed diesel particulate matter (DPM) limits split by mine type and restrictions on district managers’ authority over plans and training programs. These proposals matter because they segment obligations by underground status and commodity and may reduce plan variability across districts. Core uncertainty remains on final rule text, effective dates, and transition mechanics for removing district manager add-ons.

Background

MSHA’s July 1 proposals include: (1) reaffirming a 160 TC µg/m³ DPM limit for underground metal/nonmetal (MNM) mines and (2) retaining a 2.5 g/hour equipment emissions limit for underground coal, alongside proposals to eliminate district managers’ authority to require changes or additions to training programs and to revise roof control and ventilation plan approval criteria to remove such authority (Jackson Lewis; Federal Register; Regulations.gov; Regulations.gov). Stakeholder comments on all proposals were due July 31, 2025 (Jackson Lewis).

Key Provisions

• Underground MNM DPM exposure: MSHA proposes reaffirming the exposure-based limit of 160 micrograms of total carbon per cubic meter of air for underground MNM mines. This explicitly targets underground operations using diesel equipment and maintains the existing exposure threshold rather than introducing a new value (Jackson Lewis).
• Underground coal DPM emissions: MSHA proposes retaining the 2.5 grams per hour DPM emissions limit for diesel-powered equipment in underground coal mines. This remains an equipment-based emissions cap distinct from the MNM exposure metric (Jackson Lewis).
• Training program limits on district managers: MSHA proposes eliminating district managers’ authority to require training program content beyond statutory criteria. The training proposal applies to both surface and underground mines, indicating portfolio-wide relevance regardless of mine depth (Federal Register).
• Roof control plans: MSHA proposes revising roof control plan regulations to remove district managers’ authority to impose additional measures beyond regulatory criteria. This targets plan variability driven by district-level add-ons (Regulations.gov).
• Ventilation plans: MSHA proposes revising ventilation plan approval criteria to eliminate district managers’ authority to require additional provisions beyond the regulations. This is intended to limit site-specific plan expansions imposed during approvals (Regulations.gov).
• Timeline: Public comments on all 18 proposals were due July 31, 2025; final rule text and effective dates are pending. Implementation timing and transition mechanics are not established in the sources (Jackson Lewis).

Decision Framework

Two threshold questions drive near-term action: (1) Do you operate any underground coal mines? (2) Which sites are underground MNM with diesel exposure? A third factor is whether district managers have historically added training or plan provisions at your sites.

• If your portfolio includes underground MNM operations, then operational focus remains on the 160 TC µg/m³ DPM exposure limit. Because the proposal reaffirms this value, existing DPM exposure audits are the primary tool to avoid duplicating new processes unless the final rule adds new requirements (Jackson Lewis).
• If your portfolio includes underground coal operations, then the 2.5 g/hour DPM emissions limit continues to govern diesel equipment compliance; relying on your current equipment-based compliance checks avoids unnecessary new protocols while proposals remain pending (Jackson Lewis).
• If your training programs contain district manager–imposed add-ons, then the proposal to eliminate such authority suggests future streamlining potential; however, until finalized, maintain current approved program content and audit against it. The training proposal applies to both surface and underground mines (Federal Register).
• If roof or ventilation plans include district manager add-ons, then proposed revisions would remove that authority; transition mechanics and mine-type applicability are not provided in the filtered sources, so use existing plan-based audits pending final rules (Regulations.gov; Regulations.gov).
• Before deciding, confirm: whether any sites are underground coal; which sites are underground MNM using diesel equipment; where training and plan content include district manager add-ons; and which proposals materially apply to each site type based on the pending final texts (Jackson Lewis; Federal Register; Regulations.gov; Regulations.gov).

What We’re Monitoring

• Final rule publications, effective dates, and any phase-in periods for the DPM, training, roof control, and ventilation proposals; monitor Federal Register and docket updates (Jackson Lewis; Federal Register).
• Transition guidance on whether existing district manager add-ons become void, remain enforceable, or require operator-initiated amendments once final rules issue (Federal Register; Regulations.gov; Regulations.gov).
• Mine-type scope in final roof/ventilation plan rules to determine applicability across MNM versus coal operations (Regulations.gov; Regulations.gov).