March 11, 2013

Ken Edwards
Technical Director
Association of Equipment Manufacturers
6737 W. Washington Street, Suite 2400
Milwaukee, WI 53214

Dear Mr. Edwards:

Thank you for your July 18, 2012 letter to the Occupational Safety and Health Administration (OSHA). In this letter, you request that OSHA accept and publish the 3-6 inches allowable gap between the trench shield and trench sides as an industry standard. The allowable gap requirement is defined and discussed in your position paper, dated July 3, 2012.

We have reviewed your position paper and provide the following comments for your consideration. You have stated:

1. While your position paper indicates it is a guideline (not as a specification), you request OSHA publish the allowable gap as "an industry standard".
2. It is fairly typical to require the gap between the trench shield and trench sides to be no more than 3-6 inches.
3. Alternatively, at least the lower portion of the trench shall be backfilled (if the gap is more than 3-6 inches).

However, other trench shield manufacturers have specified the allowable gap to be no more than 12 inches for both sides of the trench shield; i.e. , if a 3 inches gap occurs on one side of the shield, the gap on the other side could be up to 9 inches. Besides, the ANSI A10.12-1998 (R2010) for Excavation does not include your proposed gap limits. Thus, there appears to be no industry consensus on the width of the gap between the trench shield and trench sides (faces).

The Agency's standard requires that trench shields be installed ". . . to restrict lateral or other hazardous movement . . . " (§1926.652(g)(ii)). The preamble to the proposed rule suggests one means of restricting movement is to minimize the gap (52 FR 12314, dated April 15, 1987). Although OSHA agrees that the closer the trench shield is to the trench side, the less likely it is to be dislodged by a lateral force, the agency would have to initiate rulemaking to require a minimum gap between the trench shield and the trench side. OSHA is unlikely to consider such a rule in its regulatory agenda.

In addition, an OSHA interpretation letter, dated October 20, 1999, to Mr. Randall addresses your concerns (copy attached). The letter states that ". . . although our standard does not set a maximum distance between a shield box and a trench face, an employer would be required to ensure that, in the event of a collapse of the face, the shield would not move laterally. " The employer is required to ensure the trench shield does not move laterally. Since the standard is written in performance language, the choice of method is up to the employer, e.g. , minimize gap, backfill gap, etc.

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 http://www.osha.gov. If you have further questions, please feel free to contact the Directorate of Construction at (202) 693-2020.

Sincerely

James G. Maddux, Director
Directorate of Construction