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 http://www.osha.gov.

August 9, 2004

Mr. Mathew McFarland
Section Manager
Consolidated Edison Company of New York, Inc.
4 Irving Place
New York, NY 10003

Dear Mr. McFarland:

This is in response to your June 11, 2004, letter to the Occupational Safety and Health Administration in which you ask for an interpretation of §1926.550(a)(15).

We have paraphrased your questions as follows:

Question (1): Is preventing electric shock or electrocution of employees the intent of §1926.550(a)(15)?

Title 29 CFR 1926.550(a)(15) states:

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

Preventing electric shock and electrocution are the purposes of the requirement.

Question (2): Some electrical distribution or transmission lines consist of an electrical conductor with a manufacturer-applied coating of insulation. In some cases that insulation is rated with a dielectric strength sufficient to prevent electrical contact. If this insulation remains intact, would this be an insulated barrier as described in §1926.550(a)(15)?

Under §1926.550(a)(15), one of the options for complying with the provision is to use an "insulating barrier." The answer to your question - whether the factory-installed insulation on the conductor is an "insulating barrier" - depends on two factors: (1) whether the employer has sufficient information to confirm that the factory-installed insulation is sufficient to prevent the passage of current and is intact, and (2) whether, in light of the circumstances (including the type of equipment and tools being used) it is reasonably foreseeable that the insulation would be damaged while doing the work.

The insulating properties (dielectric strength) of the coating must be sufficient
Typically, the type of insulation you refer to is found on some secondary lines (lines carrying nominal voltages of 480 volts or less). In most cases the employer will not be able to determine if such a line has sufficient insulating properties (both with respect to the type of insulation and its condition) to prevent electric shock and electrocution without consulting with the utility owner/operator.

Damage to the insulation must not be reasonably foreseeable
If the employer determines from the utility owner/operator that the factory-installed insulation on such a line has sufficient insulating properties to prevent electric shock and electrocution, the employer must then determine if it is reasonably foreseeable that the insulation would be damaged while doing the work. This assessment must be based on an evaluation of the tools and equipment being used and, if they were to come in contact with the line, the likelihood that the insulation would be cut or otherwise compromised. Reliance on the insulation is permitted if the insulating properties are sufficient and such damage is not reasonably foreseeable.

However, at voltages of more than 480 volts, where there is factory-installed insulation on the conductor, in most cases even slight damage could result in shock/electrocution. Consequently, for these lines, the factory-installed insulation may not be suitable for meeting this requirement. In those situations, an outer covering or external insulating barrier in addition to the factory-installed insulation would have to be used to meet the insulating barrier requirement.

Question (3): Scenario: an electrical distribution or transmission line has either a sufficient (and undamaged) factory-installed insulation as described in the previous question, or a separate, insulating barrier (such as line hose, line guards, etc.) that has been applied in the field. The minimum approach distance under §1926.550(a)(15) is 10 feet. Earth moving equipment, such as a backhoe, is being used. Such equipment is typically capable of knocking down power lines (or even a utility pole). Is it permissible in such circumstances for such machinery to work closer than 10 feet to the energized line?

Earthmoving equipment such as the equipment you describe is typically capable of knocking down power lines. Nonetheless, §1926.600(a)(6) of the Motor Vehicles, Mechanized Equipment, and Marine Operations standard states:

All equipment covered by this subpart shall comply with the requirements of §1926.550(a)(15) when working or being moved in the vicinity of power lines or energized transmitters.

By its terms, §1926.600(a)(6) permits earthmoving equipment to work within the minimum approach distance of an energized power line as long as the precautions specified in §1926.550(a)(15) are met. As explained in questions (1) and (2) above, one of the options for complying with §1926.550(a)(15) is to use an insulating barrier. Therefore, the purpose of the insulating barrier is to prevent energization of the earthmoving equipment from touching or coming too close to the energized conductor - not to prevent the line from being knocked down.

Whether the factory-installed insulation and outer covering or a line hose/guard is sufficient for purposes of complying with these provisions will depend on whether it is reasonably foreseeable that they will prevent energization of the machinery. The assessment must be made in light of the specific circumstances, including the type of protective covering used,
2 the position of the machinery (i.e., does the machinery as used present pinch points to the line?), and type of machinery surfaces involved (i.e., whether the surfaces are sharp, rounded, etc.).

In light of the above discussion, §1926.600(a)(6) does not address the hazard of shock/electrocution from machinery knocking down a power line. Under Section 5(a)(1) of the Occupational Safety and Health Act, employers are required to protect employees from recognized hazards with feasible means of protection. In the type of situation you describe, the employer must institute measures designed to protect against the line being accidentally knocked down. The measures necessary will vary depending on the circumstances. Examples of such measures may include one or more of the following: instructing the equipment operator on precise routes for the machine's operation, use of warning flags, use of a spotter, positioning equipment to minimize the risk of contact, and similar precautions.

If you need any additional information, please contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax # 202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.


Russell B. Swanson, Director
Directorate of Construction



1 A type of insulated cable for lines over 480 volts, that typically does have sufficient insulation and would not need a field-added insulated barrier, is a type that is, in effect, underground cable which is continued into the overhead system ("aerial cable"). It is supported by a "messenger system" (usually rings that hang from a steel wire). This cable has an internal conductor surrounded by insulation fully rated for the voltage, which in turn is surrounded by an outer covering. However, as with all lines, it is essential that the employer consult with the utility owner/operator to determine if the type and condition of the insulation and outer covering is sufficient. [ back to text ]





2 The fiberglass-type line hose/guard is designed to protect the line from brushing-type contact. The rubber-type line hose is less resistant to cutting-type contact then the fiberglass-type. [ back to text ]