OSHA has granted a permanent variance to CBNA/Halmar Joint Venture, the contractor building the Potomac River Tunnel Project in Washington, DC, allowing the company to use alternative decompression and compressed air safety procedures in place of standard OSHA requirements. The variance took effect December 29, 2025, and will remain in place until the project is finished or until OSHA modifies or revokes it.
Key Points
- What: OSHA permanently exempts CBNA/Halmar from standard compressed air decompression table requirements for the Potomac River Tunnel Project.
- Who: CBNA/Halmar Joint Venture workers performing hyperbaric interventions on the tunnel boring machine.
- When: Effective December 29, 2025, through project completion.
- Impact: Workers will follow alternative oxygen-based decompression protocols instead of OSHA's standard Appendix A decompression tables.
What Is This Variance?
A permanent variance is a project-specific OSHA authorization allowing an employer to use safety methods that differ from the standard rules — as long as OSHA determines those alternatives are at least as safe.
CBNA/Halmar applied for the variance in April 2024, arguing that modern tunnel boring machine (TBM) technology and advances in hyperbaric medicine make its alternative procedures safer than the decades-old OSHA decompression tables. OSHA published the preliminary approval in July 2025, received zero objections, and finalized the variance in December 2025.
What Is Changing?
OSHA's standard rules for compressed air construction work (29 CFR 1926.803) require employers to use specific decompression tables and equipment, including:
- Decompression values from Appendix A tables
- Automated operational controls
- A special decompression chamber
CBNA/Halmar will instead use oxygen-based decompression protocols managed by specialized medical personnel and hyperbaric supervisors. The company argues — and OSHA agrees — that this approach is more efficient and safer for workers.
Workers will only enter the pressurized working chamber during brief maintenance interventions, with a maximum crew of three. Pressure exposures are capped at 49.5 p.s.i.g., which stays within OSHA's existing maximum limit.
Why It Matters for the Project
Old-style compressed air tunnel work required pressurizing the entire tunnel, exposing many workers for long durations. Modern TBM technology isolates pressure to a small forward chamber, dramatically reducing the number of workers exposed and the total duration of each exposure. CBNA/Halmar's approach reflects these technological advances, which the 1926.803 standard — written for older caisson-style construction — doesn't account for.
What You Should Do
This notice has no direct relevance to F-1 students, H-1B workers, or immigration visa holders. It is a narrow, project-specific occupational safety ruling for construction workers on one Washington, DC infrastructure project. No immigration action is required or relevant here.