Depth ratings for stacked trench shields

October 29, 1991 [Reviewed May 31, 2018]

Mr. Paul Berebitski
Director, Contractor/Government Relations
Indiana Constructors, Inc.
[Recipient address omitted]

Dear Mr. Berebitsky:

Your September 25 letter to Mr. Pat Finn requesting an interpretation of the Occupational Safety and Health Administration excavation standards has been forwarded to this office for response.

In regard to your question concerning stacked trench boxes, please be advised that when trench shields are stacked in a deep trench, they do not all have to be designed to resist the forces calculated for the deepest part of the trench. The standard only requires that the shields be used at a depth not greater than that for which they are designed. To facilitate proper stacking in deep excavations, a design or system should be used to prevent the shields from being misplaced in the trench when shields of different ratings are used. Designing the shields so they will fit together only one correct way, or using a marking system that readily identifies the maximum depth each individual shield can be placed, are examples of systems that could be used to prevent such misplacement.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA's interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA's website at https://www.osha.gov. If you have further questions, please feel free to contact the Directorate of Construction at (202) 693-2020.*

Sincerely,
Patricia K. Clark, Director
Directorate of Compliance Programs
*[This letter has been modified (non-substantive changes) on May 31, 2018, and reflects current OSHA regulations and policies.]

[The requester’s September 25 letter reproduced on the OSHA page is omitted here.]