Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

February 8, 1994

Mr. Ivan Blood
St. Paul Five and Marine Insurance Company
500 W. Madison, Suite 2600
Chicago, Illinois 60661-2594

Dear Mr. Blood:

This is in response to your October 13 letter requesting an interpretation of an Occupational Safety and Health Administration (OSHA) standard addressing the operation of a crane in close proximity to overhead power lines. I apologize for the delay in responding to your inquiry.

With regard to what is acceptable as insulating barriers to prevent physical contact of equipment or machinery with electric distribution and transmission lines when the equipment or machinery is operating within 10 feet of the power lines, please be advised as follows: Rubber insulating equipment meeting the requirements of 29 CFR 1910.137 is normally intended as protection from "brushing" type contact for employees working on the lines. Although 1910.137 is not applicable to construction work, it may be used as a compliance guide for barriers required under the exception to 1926.550(a)(15), under certain conditions. If hard direct contact with the line is not likely, rubber insulating equipment can provide protection from brush contact with the power line. However, if direct impact with the lines is reasonably likely or expected, this equipment will not provide the necessary protection. In such cases, other types of barriers would be required, such as those listed in the National Safety Council Data Sheet No. 1-743New90 and the types of plastic guard equipment covered in ASTM F968, Specification for Electrically Insulating Plastic Guard Equipment for Protection of Workers. Although guards of a type consisting of ABS plastic, 1/8-inch thick, (approximate puncture strength 50,000 volts) are often successfully used on 15KV and 34.5KV systems, none are totally impact proof to the extent that strong direct blows would leave the air gap integrity unchanged or not cause sliding or other adverse movement along the line.

While the "goal post" type of guarding approach to overhead line safety probably provides the most durable means of withstanding barrier impact, it should be remembered that no practical barrier can absolutely prevent contact of a crane (or similar material handling device), simply because the capabilities of such heavy operating devices normally overwhelm any obstruction that may be installed.

If we can be of any further assistance please contact me or Dale Cavanaugh of my staff at (202) 219-8124.


Roy F. Gurnham, P.E., J.D.
Office of Construction and Maritime
Compliance Assistance


October 13, 1993

Francis Perkins Technical Data Center
Department of Labor Building
Room N 2439
200 Constitution Avenue N.W.
Washington, DC 20210

Dear Sir:

We're requesting a definitive interpretation of the following standard:


Except where electrical distribution and transmission lines have been deenergized and visibly grounded at point of work or where insulating barriers, not a part for an attachment to the equipment or machinery, have been erected to prevent physical contact with the lines, equipment or machines shall be operated proximate to power lines only in accordance with the following:

(i) For lines rated 50 kV. or below minimum clearance between the lines and any part of the crane or load shall be 10 feet;

(ii) For lines rated over 50 kV., minimum clearance between the lines and any part of the crane or load shall be 10 feet plus 0.4 inch for each 1 kV. over 50 kV., or twice the length of the line insulator, but never less than 10 feet;


What would qualify as an insulating barrier if we have a contractor, who needs to drive sheet piling adjacent to 12000V and 440V lines, where the lines are unable to be deenergized? The electric utility installed insulating barriers i.e., boot/cover, to cover the lines? Would this type of cover be acceptable when addressing the standard?

The contractor is under the assumption that when the lines are booted/covered, that he can work next to the lines and disregard the 10 foot minimal standard. We have contacted numerous OSHA compliance officers and area officers and received different interpretations. These interpretations have ranged from working a minimum of 10 feet from the energized lines to being able to work next to the energized lines.

We await your clarification on this particular issue.


St. Paul Fire and Marine Insurance Company

Ivan Blood
Account Specialist/Construction
Loss Control Services

Richard L. Hegerle
Account Specialist
Loss Control Services