CBNA/Halmar Joint Venture; Potomac River Tunnel Project; Grant of Permanent Variance

<NOTICE> DEPARTMENT OF LABOR <SUBAGY>Occupational Safety and Health Administration</SUBAGY> <DEPDOC>[Docket No. OSHA-2025-0002]</DEPDOC> <SUBJECT>CBNA/Halmar Joint Venture; Potomac River Tunnel Project; Grant of Permanent Variance</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Occupational Safety and Health Administration (OSHA), Labor. <HD SOURCE="HED">ACTION:</HD> Notice. <SUM> <HD SOURCE="HED">SUMMARY:</HD> In this notice, OSHA grants a permanent variance to CBNA/Halmar Joint Venture (CBNA/Halmar) related to work in compressed air environments. </SUM> <DATES> <HD SOURCE="HED">DATES:</HD> The permanent variance specified by this notice becomes effective on December 29, 2025 and shall remain in effect until the completion of the Potomac River Tunnel Project or until modified or revoked by OSHA. </DATES> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Information regarding this notice is available from the following sources: <E T="03">Press inquiries:</E> Contact Mr. Frank Meilinger, Director, OSHA Office of Communications, U.S. Department of Labor; telephone: (202) 693-1999; email: <E T="03">meilinger.francis2@dol.gov</E> . <E T="03">General and technical information:</E> Contact Mr. Kevin Robinson, Director, Office of Technical Programs and Coordination Activities, Directorate of Technical Support and Emergency Management, Occupational Safety and Health Administration, U.S. Department of Labor; telephone: (202) 693-1911; email: <E T="03">robinson.kevin@dol.gov</E> . </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <E T="03">Copies of this</E> <E T="7462">Federal Register</E> <E T="03">notice</E> . Electronic copies of this <E T="04">Federal Register</E> notice are available at <E T="03">http://www.regulations.gov</E> . This <E T="04">Federal Register</E> notice, as well as news releases and other relevant information, also are available at OSHA's web page at <E T="03">http://www.osha.gov</E> . <HD SOURCE="HD1">I. Overview</HD> On April 1, 2024, CBNA/Halmar Joint Venture (CBNA/Halmar or the applicant), submitted under Section 6(d) of the Occupational Safety and Health Act of 1970 (the Act), 29 U.S.C. 655, and 29 CFR 1905.11 (Variances and other relief under Section 6(d)) an application for a permanent variance from several provisions of the OSHA standard that regulates work in compressed air, 1926.803 of 1926 Subpart S—Underground Construction, Caissons, Cofferdams, and Compressed Air, and an interim order allowing it to proceed while OSHA considers the request for a permanent variance (OSHA-2025-0002-0002). This notice addresses CBNA/Halmar's application for a permanent variance and interim order for construction of the Potomac River Tunnel Project in Washington, DC only and is not applicable to future CBNA/Halmar Joint Venture tunneling projects. This notice addresses CBNA/Halmar's application for a permanent variance and interim order from the provisions of the standard that: (1) require the use of the decompression values specified in decompression tables in Appendix A of subpart S (29 CFR 1926.803(f)(1)); and (2) require the use of automated operational controls and a special decompression chamber (29 CFR 1926.803(g)(1)(iii) and (xvii), respectively). OSHA reviewed CBNA/Halmar's application for the variance and interim order and determined that they were appropriately submitted in compliance with the applicable variance procedures in Section 6(d) of the Occupational Safety and Health Act of 1970 (OSH Act; 29 U.S.C. 655) and OSHA's regulations at 29 CFR 1905.11 (Variances and other relief under section 6(d)), including the requirement that the applicant inform workers and their representatives of their rights to petition the Assistant Secretary of Labor for Occupational Safety and Health for a hearing on the variance application. OSHA reviewed the alternative procedures in CBNA/Halmar's application and preliminarily determined that the applicant's proposed alternatives, on the whole, subject to the conditions in the request and imposed by the interim order, provide measures that are as safe and healthful as those required by the cited OSHA standards. On July 24, 2025, OSHA published a <E T="04">Federal Register</E> notice announcing CBNA/Halmar's application for permanent variance, stating the preliminary determination along with the basis of that determination, and granting the interim order (90 FR 34902). OSHA requested comments on each. OSHA did not receive any comments or other information disputing the preliminary determination that the alternatives were at least as safe as OSHA's standard, nor any objections to OSHA granting a permanent variance. Accordingly, through this notice OSHA grants a permanent variance, subject to the conditions set out in this document. <HD SOURCE="HD2">A. Background</HD> The information that follows about CBNA/Halmar, its methods, and the Potomac River Tunnel Project comes from the CBNA/Halmar variance application. CBNA/Halmar is a contractor for the Potomac River Tunnel Project (the project), that works on complex tunnel projects using innovations in tunnel-excavation methods. The applicant's workers engage in the construction of tunnels using advanced shielded mechanical excavation techniques in conjunction with an earth pressure balanced micro-tunnel boring machine (TBM). Using shielded mechanical excavation techniques, in conjunction with precast concrete tunnel liners and backfill grout, TBMs provide methods to achieve the face pressures required to maintain a stabilized tunnel face through various geologies and isolate that pressure to the forward section (the working chamber) of the TBM. CBNA/Halmar asserts that it bores tunnels using a TBM at levels below the water table through soft soils consisting of clay, silt, and sand. TBMs are capable of maintaining pressure at the tunnel face, and stabilizing existing geological conditions, through the controlled use of a mechanically driven cutter head, bulkheads within the shield, ground-treatment foam, and a screw conveyor that moves excavated material from the working chamber. The forward-most portion of the TBM is the working chamber, and this chamber is the only pressurized segment of the TBM. Within the shield, the working chamber consists of two sections: the forward working chamber and the staging chamber. The forward working chamber is immediately behind the cutter head and tunnel face. The staging chamber is behind the forward working chamber and between the man-lock door and the entry door to the forward working chamber. The TBM has twin man-locks located between the pressurized working chamber and the non-pressurized portion of the machine. Each man-lock has two compartments. This configuration allows workers to access the man-locks for compression and decompression, and medical personnel to access the man-locks if required in an emergency. CBNA/Halmar's Hyperbaric Operations Manual (HOM) for the Potomac River Tunnel Project indicates that the maximum pressure to which it is likely to expose workers during project interventions for the tunnel drives is 49.5 pounds per square inch gauge (p.s.i.g.). The applicant will pressurize the working chamber to the level required to maintain a stable tunnel face, which for this project CBNA/Halmar estimates will be up to a pressure not exceeding 49.5 p.s.i.g., which does not exceed the maximum pressure specified by the OSHA standard at 29 CFR 1926.803(e)(5). <SU>1</SU> <FTREF/> CBNA/Halmar is not seeking a variance from this provision of the compressed-air standard. <FTNT> <SU>1</SU>  The decompression tables in Appendix A of subpart S express the working pressures as pounds per square inch gauge (p.s.i.g.). Therefore, throughout this notice, OSHA expresses the p.s.i. value specified by 29 CFR 1926.803(e)(5) as p.s.i.g., consistent with the terminology in Appendix A, Table 1 of subpart S. </FTNT> CBNA/Halmar employs specially trained personnel for the construction of the tunnel. To keep the machinery working effectively, CBNA/Halmar asserts that these workers must periodically enter the excavation working chamber of the TBM to perform hyperbaric interventions during which workers would be exposed to air pressures up to 49.5 p.s.i.g, which does not exceed the maximum pressure specified by the existing OSHA standard at 29 CFR 1926.803(e)(5). These interventions consist of conducting inspections or maintenance work on the cutter-head structure and cutting tools of the TBM, such as changing replaceable cutting tools and disposable wear bars, and, in rare cases, repairing structural damage to the cutter head. These interventions are the only time that workers are exposed to compressed air. Interventions in the excavation working chamber (the pressurized portion of the TBM) take place only after halting tunnel excavation and preparing the machine and crew for an intervention. During interventions, workers enter the working chamber through one of the twin man-locks that open into the staging chamber. To reach the forward part of the working chamber, workers pass through a door in a bulkhead that separates the staging chamber from the forward working chamber. The man-locks and the working chamber are designed to accommodate three people, which is the maximum crew size allowed under the permanent variance. When the required decompression times are greater than work times, the twin man-locks allow for crew rotation. During crew rotation, one crew can be compressing or decompressing while the second crew is working. Therefore, the working crew always has an unoccupied man-lock at its disposal. CBNA/Halmar asserts that these innovations in tunnel excavation have greatly reduced worker exposure to hazards of pressurized air work because they have eliminated the need to pressurize the entire tunnel for the project and ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 70k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━