Drilling near loaded blast holes

October 30, 1984

MEMORANDUM FOR: DONALD E. MACKENZIE, Regional Administrator – Region I
FROM: JOHN B. MILES, JR., Director, Directorate Field Operations
SUBJECT: Blasting Operations

This is in response to your memorandum in which you requested further clarification concerning the distance between loaded holes and the drilling of other holes as it may relate to a letter written to David Rhone, dated August 26, 1981.

Upon further consideration of this issue, we have concluded that drilling is not allowed within 50 feet of loaded holes. Drill machines are equipment within the meaning of 1926.905(h).

1926.905(h) states:

Machines and all tools not used for loading explosives into bore holes shall be removed from the immediate location of holes before explosives are delivered. Equipment shall not be operated within 50 feet of loaded holes.

1926.905(i) states:

No activity of any nature other than that which is required for loading holes with explosives shall be permitted in a blast area.

1926.905(k) states:

Holes shall be checked prior to loading to determine depth and conditions. Where a hole has been loaded with explosives but the explosives have failed to detonate, there shall be no drilling within 50 feet of the hole.

ANSI A10.7-1970 section 6.3.9 states:

No activity of any nature other than that which is required for loading holes with explosives shall be permitted in a blast area.

U.S. Army Corps of Engineers states, at Em385-1-1., 1981-25. G.03.:

Drilling and loading operations shall not be carried on in the same area. Drilling shall be separated from loaded holes by at least the depth of the loaded hole but in no case less than 50 feet.

California 1981 – OSHA Construction Safety orders state:

1566(i) Loading shall not commence until all drilling is completed and drill holes are cleaned or blown out, unless this procedure is impracticable under conditions encountered. When conditions justify simultaneous loading and drilling in the same area, the two operations shall be separated as widely as practicable and in no case less than 50 feet from drilling operations.
1566(j) No vehicle traffic shall be permitted over loaded holes.
1566(k) Loaded holes shall not be left unattended.
1567(c) Loading operations shall be carried on with the smallest practicable number of persons present, and no one but the loading crew, inspection personnel, and authorized supervisory personnel shall be allowed within 50 feet of the loading area.
1565(a) Explosives-Handling and Use. (a) Persons competent and authorized to use explosives shall be in immediate charge of all blasting. No one under 21 years of age shall be employed in loading or blasting operations, unless under the direct supervision of an experienced man.
1565(b) There shall be no smoking, open lights, or fire of any kind within 50 feet of any area where explosives are being handled. No source of ignition, except necessary means to light fuses or fire electric detonators, shall be permitted in an area containing loaded holes.

Alaska 1978 OSHA Safety and Health Explosives standards state:

89.310(b)(5) Machines and tools not used for loading explosives into bore holes shall be removed from the immediate location of holes before explosives are delivered. Equipment shall not be operated within 50 feet of loaded holes.
89.310(b)(6) No activity of any nature other than that which is required for loading holes with explosives shall be permitted in a blast area. Drilling activity shall not be carried out within 100 feet of loading operations.

Michigan OSHA 1976 Construction Safety Standards on this subject are identical to 29 CFR 1926.905(h) and (i).
Compliance officials in 24 States with approved plans have been contacted and all presently agreed with the above clarification.
[Revised 10/08/2008]