OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

January 31, 1978

Mr. Lewis J. Baker
Trial Attorney
Washington Metropolitan Area Transit Authority
600 Fifth Street, N.W.
Washington D.C. 20001

Dear Mr. Baker:

This is in response to your communication of December 8, 1977, regarding an advisory opinion concerning the applicability of 29 CFR 1926.800, tunnels and shafts. In addition, it confirms a telephone conversation with a member of my staff. I apologize for the delay in response.

A situation recently arose during METRO construction in the Washington Area that necessitated this request. It appears from your drawing No. K1-S-110. M115-132, that a cut-and-cover type tunnel construction site was partially covered to a length of approximately 200 feet. The rest of the cut was opened for a distance of approximately 400 feet. You allege an employer violated [29 CFR 1926.800(k)(10)(i)] by placing a gasoline-powered crane below ground level and under this partially covered section. This place the crane inside a configuration that appears to be about 31 feet high, 65 feet wide, 200 or more feet long, and with both longitudinal ends open.

At issue is whether the aforementioned situation is considered a tunnel and would be covered by the standard in 29 CFR 1926.800 Tunnels and Shafts. One of the standards in question [1926.800(k)(10)], states in part: ["Internal combustion engines, except diesel-powered engines on mobile equipment, are prohibited underground."]

OSHA's position is that when a cut-and-cover operation in the construction of tunnels is just an open cut, the requirements of 29 CFR 1926 Subpart P, Excavation, Trenching, and Shoring would specifically apply.

When a cover, temporary or permanent, extends over the top of the cut sufficiently to limit access or egress of employees, the movement of air, the amount of natural daylight illumination, or create other problems germane to tunnel operations, the regulations of 29 CFR 1926.800 Tunnels and Shafts, would specifically apply.

When different stages of cut-and-cover operations are concerned, careful evaluation of the employee's exposure would govern which standards are applicable.

It would be inappropriate for OSHA to make a legal determination on this particular situation with so many unknowns. Hopefully, the aforementioned guidelines will give you a good basis for reaching an opinion.

If I may be of further assistance, please feel free to contact me.


John K. Barto, Chief
Division of Occupational Safety Programming

[Corrected 05/28/2004]