U. S. Department of Labor

Occupational Safety and Health Administration

Directorate of Science, Technology and Medicine

Office of Science and Technology Assessment

Safety and Health Information Bulletin

Hazards Associated with Striking Underground Gas Lines

SHIB 03-05-21

Preface

The National Transportation Safety Board

(NTSB) reported an incident involving the

rupture of an underground natural gas pipeline

during excavation that resulted in the release

of natural gas and a subsequent explosion.1

Following their investigation, the NTSB

recommended that the Occupational Safety and

Health Administration (OSHA) “[r]equire

excavators to notify pipeline operators

immediately if their work damages a pipeline

and to call 911 or other local emergency

response numbers immediately if the damage

results in a release of natural gas or other

hazardous substance or potentially endangers

life, health, or property.”

Purpose

The purpose of this Safety and Health

Information Bulletin is:

• to remind contractors of OSHA’s

requirements to prevent accidental

damage to underground utility

installations during excavation work.

(29 CFR 1926.651(b)); and

• to recommend notifying the pipeline

operator immediately if the excavator

causes damage to a pipeline and to call

911 or other emergency response

numbers if the damage results in a

release of natural gas or other

hazardous substances.

Background

On December 11, 1998, while attempting to

install a utility pole support anchor in a city

sidewalk in St. Cloud, Minnesota, a cable

construction company installation crew struck

and ruptured an underground, 1-inch-diameter,

high-pressure, plastic gas service pipeline,

resulting in a natural gas leak. Approximately

39 minutes later, while utility workers and

emergency response personnel were assessing

the situation and taking preliminary steps to

1

National Transportation Safety Board. 2000. Natural Gas Pipeline Rupture and Subsequent Explosion in St. Cloud,

Minnesota, December 11, 1998. Pipeline Accident Report NTSB/PAR-00/01. Washington, D.C.

www.nstb.gov/publictn/PAR0001.htm

This Safety and Health Information Bulletin is

not a standard or regulation, and it creates no

new legal obligations. The Bulletin is advisory

in nature, informational in content, and is

intended to assist employers in providing a safe

and healthful workplace. The Occupational

Safety and Health Act requires employers to

comply with hazard-specific safety and health

standards. In addition, pursuant to Section

5(a)(1), the General Duty Clause of the Act,

employers must provide their employees with a

workplace free from recognized hazards likely

to cause death or serious physical harm.

Employers can be cited for violating the General Duty Clause if there is a recognized hazard

and they do not take reasonable steps to prevent or abate the hazard. However, failure to

implement these recommendations is not, in

itself, a violation of the General Duty Clause.

Citations can only be based on standards,

regulations, and the General Duty Clause.
2

stop the gas leak, an explosion occurred. As a

result of the explosion, 4 persons were fatally

injured; 1 person was seriously injured; and 10

persons, including 2 firefighters and 1 police

officer, received minor injuries. Six buildings

were destroyed.

Incident Description

The cable construction company installation

crew was installing a utility pole support

anchor in a city sidewalk. They struck and

ruptured an underground, high-pressure gas

service pipeline, resulting in a natural gas leak.

Within a minute of striking the gas line, the

company crew foreman, following company

procedures, informed his supervisor. However,

the supervisor did not immediately notify the

owner of the gas line or emergency response

agencies. About 15 minutes after the gas line

was struck, another individual, who was not

associated with the construction project,

notified emergency responders. The supervisor

called the owner of the gas line about 30

minutes after the line was struck.

A fire truck and four firefighters were on the

scene about 18 minutes after the rupture and

about 2 minutes after being notified. Two

power company employees, a gas technician

specialist, and a utility locator technician,

having been notified by the fire department,

arrived on the scene about 26 minutes after the

pipeline was ruptured.

The gas technician specialist entered the

basement of a nearby building, which housed a

deli and a pizza restaurant. While the gas

technician specialist was taking readings with a

combustible gas monitor, the locator technician

was determining whether the service line was

properly marked. Approximately 39 minutes

after the gas line was struck, the explosion

killed the gas technician specialist, the utility

locator technician, one person in the building,

and a nearby pedestrian. A three-person power

company construction crew, which had been

dispatched to shut down the damaged portion

of the line, was still 2 blocks away from the

accident site when the explosion occurred.

According to the report of the Minnesota Fire

Marshal, the explosion occurred in the

basement of the building that housed the pizza

restaurant and deli. The report could not

identify the source that ignited the gas that was

accumulated in the basement. However,

potential ignition sources included gas water

heaters.

The NTSB determined that the accident was

related to the lack of adequate procedures by

the cable construction company to prevent

damage to underground utilities when

excavating. Contributing to the severity of the

accident was the company’s delay in notifying

the utility operator and proper authorities.

The Minnesota OSHA, Minnesota Department

of Labor and Industry, investigated the accident

and cited the cable construction company for

violating workplace safety programs, the

Minnesota General Duty Clause, and

excavation requirements (29 CFR 1926. 651(b)

standard).

Other Information

In 1997, NTSB published a safety study that

discussed industry and government actions to

prevent excavation damage.2

 The study

concluded that, at a minimum, “excavators

should formulate an emergency response plan

appropriate for the specific construction site

and ensure that employees working at that site

know the correct action to take if a buried

facility is damaged.”

2

National Transportation Safety Board. 1997. Protecting Public Safety Through Excavation Damage Prevention. Safety Study

NTSB/SS-97/01. Washington, D.C. www.nstb.gov/publictn/1997/ss9701.htm
3

The safety study referred to a previous safety

recommendation, NTSB P-95-25, issued to the

American Public Works Association (APWA)

following a 1993 NTSB accident investigation

in St. Paul, Minnesota. NTSB P-95-25

recommended that the APWA urge its

“members to call 911 immediately, in addition

to calling the gas company, if a natural gas line

has been severed.”

In August 1999, the Department of

Transportation published Common Ground:

The Study of One-Call Systems and Damage

Prevention.3

 The report recommended that “if

the protective coating of an electrical line is

penetrated or gases or liquids are escaping

from a broken line which endangers life, health

or property, the excavator [should] immediately

contact local emergency personnel or call 911

to report the damage location.”

The National Utility Locating Contractors

Association (NULCA) has published

guidelines for excavation practices and

procedures for damage prevention. These

guidelines suggest that excavators call 911 if

excavation damage “involves a potential risk to

life, health or significant property damage.”

The State of Minnesota revised Minnesota

Statute 216D, effective August 1, 1999. The

law states, in part:

“If any damage occurs to an underground

facility or its protective covering, the excavator

shall notify the operator promptly. When the

operator receives a damage notice, the operator

shall promptly dispatch personnel to the

damage area to investigate. If the damage

results in the escape of any flammable, toxic,

or corrosive gas or liquid or endangers life,

health, or property, the excavator responsible

shall immediately notify the operator and the

3

The Common Ground report was prepared by more than 160 individuals representing a wide range of interests, organizations,

and viewpoints. The report focuses on preventing damage to underground facilities. The project was initiated by the U.S.

Department of Transportation’s Office of the Pipeline Safety, an element of the Research and Special Programs Administration,

in response to the Transportation Equity Act for the 21st Century, Public Law 105-78, enacted on June 9, 1998. The purpose of

the year-long study was to identify and validate existing best practices to prevent damage to underground facilities.

911 public safety answering point...and take

immediate action to protect the public and

property.” (Emphasis added)

OSHA Standards

OSHA’s 29 CFR 1926.651 standard establishes

specific excavation requirements designed to

protect employees and prevent accidental

damage to underground utility installations.

The requirements include:*

• Establishing the location of

underground installations prior to

opening an excavation;

• Contacting utility companies or owners

within established or customary local

response times. When utility

companies or owners cannot respond to

a request to locate underground utility

installations within 24 hours or cannot

establish the exact location of these

installations, the employer may proceed

with caution using detection equipment

or other acceptable means to locate

utility installations;

• When approaching the estimated

location of underground installations,

the exact location of the underground

installations shall be determined by safe

and acceptable means; and

• While the excavation is open,

underground installations shall be

protected, supported, or removed as

necessary to safeguard employees.
4

Conclusions

Excavators need to: establish a detailed work

plan and train their employees prior to

excavating on the proper procedures of

determining the locations of underground

utilities; contact and coordinate with the

utilities companies to establish the locations

of the underground installations; and take all

necessary precautions to prevent damaging

underground utility installations.

If an underground utility is damaged, the utility

operator is in the best position to determine the

hazards associated with the damage and

implement appropriate countermeasures.

OSHA recommends that the excavator notify

the utility operator promptly. If the damage

results in the release of hazardous gases or

liquids, both the utility operator and appropriate

emergency response officials should be notified

immediately.

* Please refer to the Code of Federal

Regulations for the full text of the

requirements.