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.

March 23, 1992 [Reviewed November 8, 2018]

Mr. George Kennedy, C.S.P.
Director of Safety
National Utility Contractors Association
137 Ruhle Road
Ballston Spa, New York 12020

Dear Mr. Kennedy:

This is in response to your September 20 request for interpretation of the Occupational Safety and Health Administration (OSHA) construction standards addressing excavations. I apologize for the delay in responding to your inquiry.

In regard to whether workers can enter a trench with water accumulation if the workers are protected from cave-in by shoring, shields or sloping and the water level is controlled, please be advised by the following: Paragraph .651(h) of 29 CFR 1926 allows workers to work in a trench with water accumulation, provided adequate precautions have been taken to protect employees against the hazards posed by water accumulation. The precautions necessary to comply with the standard vary with each situation, and the precautions you listed, such as additional shoring and control of the water level may not, in all cases, provide the required employee protection.

In regard to whether a stairway or ladder is required at points of access to a trench where there is a break in elevation of 19 inches or more, please be advised that since the specific excavation standard also addresses means of access and egress, the more general requirement in the stairways and ladders subpart is not applicable. A ladder, stairway, ramp or other safe means of access is required only when the trench is four feet or more in depth. Please be advised that Paragraph 651(c)(2) also states…as to require no more than 25 feet (7.62 m) of lateral travel for employees.*

In regard to whether emergency rescue equipment is required at every trenching jobsite located near or passing by a gas station, refinery, gas line, sewer main, etc., please be advised by the following: Emergency rescue equipment is required to be readily available where a competent person determines, based on the conditions at each jobsite, that hazardous atmospheric conditions exist or may reasonably be expected to develop during work in an excavation. In regard to whether a contractor can rely on a local rescue squad instead of providing the rescue equipment, please be advised that many emergency situations associated with the hazards involved with hazardous atmospheres in trenches would normally require an immediate response within a few minutes or even seconds. A rescue squad would be unable to provide the necessary response and therefore could not be used to comply with 1926.651(g)(2).

In regard to whether a contractor must have separate manufacturer's tabulated data on hand for each specific shield, please be advised that only one set of tabulated data is required for each different shield design. If a contractor uses several shields of the identical make and model, only one set of tabulated data would be required for them.

In regard to whether manufacturer's tabulated data can be used to design protective systems for trenches more than 20 feet in depth, please be advised as follows: Protective systems that are designed using manufacturer's tabulated data can be used in trenches deeper than 20 feet provided the use is within the limits of the data, including depth limitations and soil type. It should be noted that all tabulated data, by definition (1926.650), must be approved by an RPE. (See 1926.652(c)(2).)*

In regard to the need to recertify protective systems that have been damaged or repaired, please be advised as follows: Shields or other protection systems, damaged to the extent that the structural integrity or the ability of the system to perform as designed is affected, cannot be used until repaired and recertified by a Registered Professional Engineer (RPE) or the manufacturer of the system. Minor repairs or normal maintenance done in accordance with manufacturers specifications do not need recertification. (See 1926.652(d)(3).)*

In regard to how ladders must be secured in trenches, please be advised that paragraphs 1926.1053(b)(6) and (7) address ladder footing displacement which is not normally a problem in trenches. If a ladder needs to be secured against tipping, it may be secured to a shield or member of a protective structure provided the ladder does not alter the effectiveness of the protective system.

In regard to whether a competent person must be present at a trench at all times, please be advised that it is not normally necessary for a competent person to be at a jobsite at all times. However, it is the responsibility of a competent person to ensure compliance with applicable regulations and to make those inspections necessary to identify situations that could result in possible cave-ins, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions, and then to insure that corrective measures are taken. Consistent with these goals, the competent person may perform other duties. (See 1926.651(k)(1).)*

In regard to whether an RPE must approve all work when digging below a footing, foundation, retaining wall, sidewalk or pavement, please be advised by the following: An RPE approval is not required when the excavation is not "reasonably expected to pose a hazard to employees." In situations where it is reasonably expected to pose a hazard, an RPE approval is not required when a support system, such as underpinning, is provided to ensure the safety of employees and the stability of the structure, or the excavation is in stable rock. (See 1926.651(i)(2).)*

In regard to the conditions under which OSHA would consider a trench a confined space, please be advised that under normal circumstances, a trench would not be considered a confined space. The excavation standards address the hazards associated with employees entering potentially harmfully atmospheres by requiring atmospheric testing and controls where hazardous atmospheres exist or could reasonably be expected to exist.

In regard to trenching along a hillside where the trench walls are at different heights, a contractor must provide a support system that will withstand the forces present at the bottom of the deepest side, or rely on a protective system approved by an RPE. (See 1926.652(a)(1).)*

In regard to whether OSHA will accept a thumb test when estimating the compressive strength of soil, please be advised that the thumb penetration test is one of the acceptable methods of estimating soil compressive strength. The compressive strength can be determined by laboratory testing, or estimated in the field using a penetrometer, shear vane, thumb penetration tests, as well as by other methods. (See Appendix A of Subpart P.)*

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.*


Patricia K. Clark, Director
Directorate of Compliance Programs

*[This letter has been modified (non-substantive changes) on November 8, 2018, and reflects current OSHA regulations and policies.]




September 20, 1991





Mr. Roy Gurham
Director of Compliance Assistance
U.S. Dept. of Labor - OSHA
200 Constitution Ave., N.W.
Room N3610
Washington, D.C. 20210

Dear Roy,

Our members are concerned about the way the Excavation Standard is being interpreted in different parts of the country. They have requested that I contact you to have some parts of the standard clarified.

If possible, please provide me with interpretations for the following questions, so that I can disseminate it to our members.

1. Can workers enter a trench with water accumulation if the workers are protected from cave-in by shoring, shields or sloping, and the water level is controlled?

2. The Stairways and Ladders Standard requires that a stairway or ladder shall be provided at points of access where there is a break in elevation of 19 inches or more. The Excavation Standard requires a ladder or other means of access and egress when the trench is 4 feet or more. Which of these requirements is applicable to trenching operations?

3. Must rescue equipment be available at every trenching jobsite that is located near of passes by a gas station, refinery, gas line, sewer main, etc? Can a contractor rely on the local rescue squad since they are probably better equipped to handle a rescue?

4. If a contractor has several of the same make and model trench shields at a jobsite, does he have to have separate manufacturer's tabulated data on hand for each specific shield? We have been told that the shields and the data sheets must have the same serial number in order to be in compliance.

5. Do excavations greater than 20 feet have to be designed by an RPE or can manufacturer's tabulated data be used in lieu of an RPE? For example, a contractor may have boxes rated for depths greater than 20 feet.

6. Does a RPE have to recertify a trench shield if the skin is patched? If the rail from an aluminum hydraulic shoring system is bent slightly out of shape, does it have to be removed from service, repaired and recertified by an RPE? At what point does and RPE have to recertify equipment that has been repaired?

7. We clearly understand that a ladder has to be secured, but we are not sure how. Contractors have informed us that compliance officers have told them that they can not secure a ladder to the shoring system or in some cases the trench shield. These same contractors have been told to secure the ladder by driving a stake into the ground and to tie the ladder off to the stake. This alternate method presents three different problems: 1) It is not always possible to drive a stake through concrete or asphalt sidewalks or pavement; 2) This method creates a tripping hazard next to the trench; 3) Some contractors believe that driving a stake could create a stress crack. Please clarify these requirements for us?

8. Does the competent person have to be standing by the trench at all times during the work shift or can he/she go off site for short periods of time, such as lunch, meeting, or maybe to pick up supplies at the local builders supply store? Can the competent person move around the jobsite away from the trench? often the foreman is the competent person and he may have other responsibilities at the jobsite.

9. Must a RPE approve all work when digging below a footing, foundation, retaining wall, sidewalk or pavement? We recognize the need for an RPE to design a system to support buildings and structures. However, we don't agree that an RPE is needed to layout a system to support sidewalks, pavement, and in some cases small structures like a small retaining wall. It is often very difficult to find an RPE who is willing to take on small incidental projects.

10. At what point and under what conditions would OSHA consider a trench a confined space?

11. When trenching along the side of a hill, what criteria should a contractor use to determine the depth of the trench?

12. Some compliance officers are telling contractors that they must use a penetrometer or shearvane to estimate the compressive strength of soil and that the thumb test is unacceptable. Keeping in mind that these are field tests. We realize that the thumb test is not accurate, but neither is the penetrometer that many compliance officers swear by. What is OSHA's interpretation for using a thumb test versus an instrument?

These questions are common and in several cases contractors have been cited. We are concerned and want to make sure our members clearly understand the regulations.

Thank you for your assistance.


George S. Kennedy, CSP
Director of Safety

P.S. Please send your reply to me at:
137 Ruhle Road,
Ballston Spa, NY 12020