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.

October 1, 2010

Letter #20061017-7300

Re: Applicability of Subpart S to tunnels constructed by auger boring.

This is in response to your letter dated October 17, 2006, to the Occupational Safety and Health Administration (OSHA).  You ask about the application of the underground construction standard, 29 CFR 1926.800, to an auger boring operation.  We apologize for the long delay in responding.

We have paraphrased your questions as follows:

Question: When constructing a sewer or water line tunnel using an auger bore, employees must sometimes enter the section of the bore in which casing has been installed in order to clear blockages, check pipe alignment, cut wings with a torch to steer the casing, and perform other tasks.  These tasks occur prior to when all the casing has been installed.  In this circumstance, when employees enter the casing, is 1926 Subpart S applicable?

Answer: We understand the scenario you have described as an operation in which structural casing sections are forced into the bore made by the auger.  This is a type of "pipejacking" operation; in a May 28, 1998 letter, OSHA defined pipejacking as:

A method of installing pipe or other lining where the section of lining is installed at the opening of the excavation and is jacked or otherwise forced towards the advancing face.

The scope of 1926 Subpart S (Underground construction) is defined by 29 CFR 1926.800(a)(1), which states:

"This section applies to the construction of underground tunnels, shafts, chambers, and passageways..."

Pursuant to §1926.800(a)(1), for Subpart S to apply, the tunnel or shaft must be under "construction."  In the pipejacking scenario you refer to, on occasion, employees enter the casing that has already been jacked into place, but before the bore has been completed and all the casing has been installed.  In short, they enter during the period in which a tunnel is being constructed by progressively installing structural casing; they enter while the tunnel or shaft is under "construction."

This conclusion is reinforced by the preamble to this rule.  In discussing the rule's scope, OSHA stated:

OSHA also intends to apply these rules to certain pipejacking operations, based on the location of the employees performing the work.  For example, if an employee is working underground, then this section applies, regardless of whether the ground support is advanced by pushing pipe or is fabricated within the heading.  However, if an employee is working outside of the portal in an open pit (for example, operating horizontal boring and pipejacking equipment) and is not exposed to underground construction hazards, then this section does not apply.  (That type of an operation is more appropriately covered by other OSHA construction standards, including Excavations (§1926.652) and Confined Spaces (§1926.21(b)(6).) [Volume 54 of the Federal Register, page 23826; emphasis added].

In sum, the Agency determined in the rulemaking that Subpart S applies when an employee is underground during the construction of a tunnel where pipejacking takes place1. Whether or not an employee is "continuously" underground does not affect the application of the rule.  When an employee is engaged in the type of pipejacking you describe and enters the casing while it is under construction for any period, Subpart S applies.

Additionally, you compare the operation you describe as similar to an employee "entering a manhole."  The preamble to this rule states:

OSHA intends that §1926.800 protect employees working in both pre-existing manholes and manholes under construction if the manhole is both physically connected to an active underground construction operation and also covered to such an extent that the manhole presents the underground construction hazards addressed in this section. [Volume 54 of the Federal Register, page 23826].

Therefore, Subpart S applies when a manhole connects to an active underground construction operation and conditions expose an employee within the manhole to hazards typical of underground construction.

If you have any questions about this response, or need further clarification on this subject, please contact us by fax at (202) 693-1689.  You may also contact us by mail at the U.S. Department of Labor, Directorate of Construction, Office of Construction Standards and Guidance, Room N-3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210.

Thank you for your interest in occupational safety and health.


Ben Bare, Acting Director
Directorate of Construction

1  As explained above, Subpart S also applies if the employee is outside the portal while exposed to typical underground construction hazards. [Return to Text]