During the1999 National Electrical Code (NEC) cycle, Code-Making Panel 3 (CMP-3) accepted a revision to Section 300-5(d) that reads: “Service laterals that are not encased in concrete and that are buried 18 inches (457mm) or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 12 inches (305mm) above the underground installation.”

This requirement entered the Code through an unusual route. The original proposal was submitted to CMP-4 because the requirement was applicable to service laterals only and CMP-4 has jurisdiction for Article 230, Services. CMP-4 however, rejected the original proposal and recommended that the Technical Correlating Committee forward it to CMP-3 for action during the Comment stage of the 1999 NEC cycle. Despite the limitation to service laterals, CMP-3 accepted the proposal as a new second paragraph to Section 300-5 (d) Protection from Damage.


As was indicated in the substantiation for the proposal, the purpose of this requirement is to provide a warning ribbon in trenches to alert the worker of the presence of underground electrical conductors. Because these conductors are often “unprotected,” they offer increased electrical risks to all personnel. The requirement was carefully worded so that its applicability would only protect conductors only in installations where the depth of the excavation was sufficient to allow for adequate warning before the conductors were contacted.


CMP-4 rejected the original proposal only because they believed it was beyond the scope of their panel. When the proposal arrived at CMP-3, there was broad support. The only concern expressed was whether the electrical contractor or the electrical utility would be installing service laterals and whether the electrical utility would be required to meet this provision. In addition, CMP-3 discussed whether the scope of the proposal should be expanded to include feeders or branch circuits that are located underground, and not just service laterals. CMP-3 unanimously accepted the proposal as submitted. Regarding the limitation to service laterals, CMP-3 in their panel statement stated that, since Article 300 applies to all wiring methods, the specific requirement for service laterals was proper in Article 300.

2002 NEC

For the 2002 NEC, CMP has rejected several proposed revisions seeking to expand the application beyond service laterals to include feeders and branch circuits. Although feeders and branch circuits are “protected” conductors in the sense of overcurrent protection, hazards associated with digging into these conductors still exist, whether or not they are defined as service, feeder, or branch circuit conductors.


Electrical contractors installing service lateral conductors must install a warning ribbon when the trench is at least 18 inches deep and the conductors are not encased in concrete.

Note that the requirement is performance, not specification oriented. How the warning ribbon is installed, the color, the type of the ribbon, etc., is left to the contractor.

In addition, electrical contractors who dig where contact with underground utility lines is possible, including electrical, sewer, gas, etc., must adhere to Occupa-tional Safety and Health Administration (OSHA) regulations covering excavations. For example, Section 1926.651 (b)(1) requires that, “(T)he estimated location of utility installations, such as sewer, telephone, fuel, electric, water lines, or any other underground installations that reasonably may be expected to be encountered during excavation work, shall be determined prior to opening an excavation.”

Section 1926.651 (b)(2) of the OSHA regulations state “(U)tility companies or owners shall be contacted within established or customary local response times, advised of the proposed work, and asked to establish the location of the utility underground installations prior to the start of actual excavation. When utility companies or owners cannot respond to a request to locate underground utility installations within 24 hours (unless a longer period is required by state or local law), or cannot establish the exact location of these installations, the employer may proceed, provided the employer does so with caution, and provided detection equipment or other acceptable means to locate utility installations are used.”

These laws can vary dramatically. Pay particular attention to the accuracy requirement for the approximate location of the lines; in some states, this can be as much as 36 inches to either side of the estimated location. Always use suitable detection equipment and hand digging when the exact location cannot be determined.

CMP-3 is right to revisit this important requirement. Many considerations remain to be discussed and debated until a workable and enforceable rule that provides the greatest level of protection for employees and the public is achieved.

CALLANAN is director of Safety, Codes, and Standards at the National Joint Apprenticeship & Training Committee. He can be reached at mic3@concentric.net.