Construction blasting equipment and drilling near loaded holes

April 1, 1982

Commissioner Robert Beard
Department of Labor and Industries
[Recipient address omitted]
Dear Commissioner Beard:

This is in response to your telephone inquiry of March 22, 1982, to our office of Construction and Civil Engineering Safety Standards, requesting a clarification of the intent of 29 CFR 1926.905(h) and (k).

The two parts of paragraph (h) address first any vehicles, earthmoving machines, and associated equipment not required for that part of the work related to loading the holes or blast preparation, such as fly rock prevention. The second sentence addresses all other construction or haulage equipment whether related to the blasting operations or something else. It is recognized that in certain work, drills, jumbos and bulk blasting agent vehicles are used in relation to the loading of blast holes.

Paragraph (k) addresses the 50 foot distance in which drilling is prohibited if a loaded hole failed to detonate. However, the regulations do not say how close to a loaded hole drilling can ordinarily be performed. The proximity to a loaded hole that drilling can be performed is dependent upon the type of explosives used (its sensitivity), the type of detonating system, whether there is overburden, whether the drill or drill vehicle can be controlled suitably to preclude intersecting or disturbing the loaded hole, or anything that would cause a misfire or premature initiation. When these things are determined, drilling proximity distance can be established. The object of the regulation is to reduce the potential for premature initiation or blasting components and resultant employee injury.

If I may be of further assistance, please feel free to contact me.

Sincerely,
Patrick R. Tyson
Director,
Federal Compliance and State Programs