OSHA Grants Variance for Potomac River Tunnel's Compressed Air Operations
Published Date: 12/29/2025
Notice
Summary
OSHA has given CBNA/Halmar Joint Venture a permanent green light to work in special compressed air conditions for the Potomac River Tunnel Project in Washington, DC. This change lets them follow different safety rules until the project wraps up, starting December 29, 2025. Workers on this tunnel project are affected, and the variance helps keep the work moving smoothly without extra delays or costs.
Analyzed Economic Effects
5 provisions identified: 5 benefits, 0 costs, 0 mixed.
Permanent variance for Potomac Tunnel
OSHA granted CBNA/Halmar a permanent variance that takes effect on December 29, 2025 and stays in place until the Potomac River Tunnel Project is finished or OSHA modifies or revokes it. The variance applies only to CBNA/Halmar and only to construction work on the Potomac River Tunnel Project and affects workers who enter the pressurized working chamber.
Use of 1992 French decompression tables
CBNA/Halmar may use the 1992 French Decompression Tables (including staged decompression with air and/or pure oxygen) instead of OSHA's decompression tables for compressed-air workers. OSHA's notice states oxygen-assisted decompression can reduce decompression time by about 33 percent and that a physician certified in hyperbaric medicine will manage worker medical care.
Manual staged decompression under supervision
Instead of automatic continuous decompression controllers, CBNA/Halmar will use staged decompression carried out under a trained man-lock attendant and overseen by a hyperbaric supervisor and an attending physician certified in hyperbaric medicine. OSHA determined this manual, staged approach is at least as effective as automatic continuous controls.
Man-locks replace special decompression chamber
Because space in the tunnel-boring machine (TBM) is limited, CBNA/Halmar may use the TBM’s twin man-locks and staging chamber in place of a separate special decompression chamber. The permanent variance limits the maximum crew in the working chamber to three people and the TBM arrangement is described as able to safely accommodate decompression times (the notice references decompression up to 360 minutes in the conditions discussion).
Stronger safety paperwork and prompt reporting
CBNA/Halmar must submit a project-specific Hyperbaric Operations Manual (HOM) and proof of compliance with ASME PVHO-1 at least six months before using the TBM, keep detailed records of hyperbaric interventions (including completing OSHA Form 301), notify OSHA within 24 hours of hyperbaric recordable incidents and provide a copy of the incident report, and notify OSHA's OTPCA and the Baltimore/Washington Area Office within 15 working days if it needs to revise the HOM.
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