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.

June 22, 1999

William Clouston
Mining Engineering Technician
Panama Canal Commission
ECDB Unit 2300
APO AA 34011-2300

Dear Mr. Clouston:

This is in response to your letter of July 15,1998, to the Occupational Safety and Health Administration's (OSHA) Office of Construction Standards and Compliance Assistance. You raised questions about OSHA requirements with respect to the use of earthmoving equipment for several blasting operation activities: the stemming of boreholes, recovery of stuck vehicles and clearing mud within the shot perimeter.

Section 1926.905(h) prohibits the use of all equipment not used for loading explosives in the immediate location of boreholes and the operation of equipment within 50 feet of a loaded borehole. The only exempted equipment is that which is used to load explosives into boreholes.

You describe a situation where you are doing wet blasting under wet, muddy conditions. You are having trouble with your bulk vehicles getting stuck in the mud. You are currently using a Cat D-5 tractor to pull other equipment, including the payloader that is loaded with stemming material, away from the loaded bore holes. You ask if the standard allows you to use a payloader for stemming operations and if you can use the D-5 tractor to recover the stuck payloaders within the shot perimeter.

The purpose of the standard is to prevent equipment from causing unplanned detonations. Earthmoving equipment can cause such detonations in several ways. These include introducing an electric ignition source and causing detonation by compaction from the weight of the vehicle.

The requirement of the standard does apply to work in the type of severe work environment you describe. The standard does not prohibit the use of machines, including payloaders, for loading explosives but your payloaders may not be well suited for the conditions of your operation. Operating the tractor within the vicinity of a loaded bore hole is in violation of the standard. Changes to the stemming and explosives loading pattern, reducing the number of bore holes, and use of earthmoving equipment more suitable to wet, muddy conditions would be ways of addressing the problem you describe within the constraints of the regulation.

If you require any further assistance, please do not hesitate to contact us again by writing to: the Office of Construction Standards and Compliance Assistance, Directorate of Construction - OSHA, Room N3621, 200 Constitution Avenue, N.W., Washington, D.C. 20210


Russell B. Swanson
Directorate of Construction