Trench-box position during pipe backfilling

July 29, 2005 [Reviewed November 22, 2017]

David McClintock

President

IKOCPA, Ohio Executive Committee

[Recipient address omitted]

Re: Adjusting work practices to comply with cave-in protection requirements in §1926.652, Requirements for protective systems in excavations.

Dear Mr. McClintock:

This is in response to your letter dated November 15, 2004, to Richard Gilgrist, the Cincinnati Area Director for the Occupational Safety and Health Administration (OSHA). Your letter was forwarded to the Directorate of Construction, Office of Construction Standards and Guidance for response. We appreciate the additional information you provided in our telephone calls with you. We apologize for the delay in our response.

We have paraphrased your question as follows:

Question (1): Scenario: An 18-inch diameter (or larger) plastic pipe is installed in an excavated trench deeper than 5 feet. The trench has a layer of "bedding" material, which is typically crushed stone, which the pipe rests on. After the pipe is installed, backfill material (crushed stone) is added, which extends from the bedding to about 12 inches above the top of the pipe. During the process of installing the pipe, in accordance with Part 1926 Subpart P, a trench box is used.

One of the work practices used in this type of project is to use an excavator to drag the trench box to the next location after the backfill has been added. ASTM D2321 sections 6.4.1 and 6.4.2 recommend not disturbing the backfill when using a movable trench box and/or shield. In some cases, some contractors have found that if the trench box is installed in accordance with §1926.652(g)(2) - that is, no more than 2 feet above the bedding material - a problem arises.

With the trench box no more than 2 feet above the bedding, once the backfill is added the trench box walls wind up below the surface of the backfill. When the trench box is dragged to the next location, the backfill sloughs off into the space previously occupied by the trench box walls and the pipe loses the support provided by the backfill. Consequently, some contractors want to install the trench box higher than 2 feet above the bedding to avoid disturbing the backfill (see illustration below).

There seems to be a conflict between ASTM D2321 and §1926.652(g)(2). Does such a conflict mean that this work practice is permissible under §1926.652(g)(2)?

Answer: No, it is not permissible if workers are in the trench when the trench box is more than 2 feet above the bedding. 29 CFR 1926.652(g)(2) states:

Excavations of earth material to a level not greater than 2 feet (0.61 m) below the bottom of a shield shall be permitted, but only if the shield is designed to resist the forces calculated for the full depth of the trench, and there are no indications while the trench is open of a possible loss of soil from behind or below the bottom of the shield.

The employer would have to adjust its work practices to ensure that the requirements of §1926.652(g)(2) are met. Our understanding is that there are several ways an employer could comply with the OSHA requirements (§1926.652(g)(2)) and ensure the pipe is adequately supported. For example, in the scenario you described, the employer could meet both the requirements of §1926.652(g)(2) and the ASTM recommendation by removing the employees in the trench before raising the trench box more than 2 feet. With the employees removed, there would be no employee exposure to the cave-in hazard while the trench box was lifted and moved, and therefore no violation of §1926.652(g)(2). Once the box is in its new position (and set less than 2 feet above the working surface, the employees could re-enter the trench.

Question (2): What is the penalty for violating §1926.652(g)(2)?

Answer: In accordance with Section 17 of the Occupational Safety and Health Act of 1970 and 29 CFR 1903.15(d), the maximum penalty that may be assessed for a single, non-criminal violation of this requirement is $126,749. [Maximum penalties adjusted as of January 15, 2017] The penalty assessed in a particular case may be equal to or less than that amount, depending on a number of factors. These factors include whether the violation is classified as "willful," "repeated," "serious" or "other than serious." Other factors that may also affect the penalty assessment include the gravity of the violation, the size of the business of the employer being cited, the good faith of the employer and the employer's history, if any, of previous violations.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA requirements are set by statue, standards, and regulations. Our letters of interpretation do not create new or additional requirement but rather explain these requirements and how they apply to a 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 impact 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,

Russell B. Swanson, Director

Directorate of Construction

cc: Michael Connors, Regional Administrator

*[This letter has been modified (substantive changes) on November 22, 2017, and reflects current OSHA regulations and policies .]