OSHA Bends Rules for Cleveland's Deep Tunnel Diggers
Published Date: 12/29/2025
Notice
Summary
OSHA gave McNally Tunneling Corp./ASI Marine a permanent green light to work in compressed-air conditions for their Southerly Tunnel project in Cleveland. This special permission starts December 29, 2025, and lasts until the project wraps up or OSHA changes its mind. It means McNally/ASI Marine can keep digging safely with some relaxed rules, helping the job move along without costly delays.
Analyzed Economic Effects
5 provisions identified: 3 benefits, 0 costs, 2 mixed.
Allowed Compressed-Air Pressure Raised
OSHA gave McNally/ASI Marine permission to expose workers to compressed-air pressures up to 58 p.s.i.g. during interventions in the TBM for the Southerly Tunnel project. This permission is effective December 29, 2025 and lasts until the project is finished or OSHA modifies or revokes the variance.
Use of 1992 French Decompression Tables
McNally/ASI Marine may use the 1992 French Decompression Tables (including oxygen-assisted staged decompression) instead of OSHA's Appendix A decompression tables for workers on the Southerly Tunnel project. The company says the alternative can reduce decompression time by about 33 percent and lower decompression-illness rates when applied with trained medical supervision.
Manual Staged Decompression Allowed
Instead of requiring automated continuous decompression controllers, the variance allows staged (manual) decompression under the direct control of trained man-lock attendants and oversight by a hyperbaric supervisor and certified physician for the Southerly Tunnel project. OSHA found this manual staged approach, with the stated safeguards, to be at least as effective as automatic controls.
Man-Locks Replace Special Chamber
Because of TBM space limits, the variance allows use of the TBM's twin man-locks and the staging chamber instead of adding a separate special decompression chamber for the Southerly Tunnel project. The man-locks and staging chamber must accommodate the maximum crew of three and allow movement during decompression, including when decompression exceeds 75 minutes.
Variance Limited to McNally/ASI Southerly Project
The permanent variance applies only to McNally Tunneling Corp./ASI Marine and only to the remainder of construction work on the Southerly Tunnel and Consolidation Project in Cleveland. It does not apply to other McNally/ASI Marine tunneling projects or other employers.
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