St. Cloud, Minnesota
December 11, 1998
NTSB Number: PAR-00-01
NTIS Number: PB2000-916501
Adopted July 11, 2000
About 10:50 a.m. on December 11, 1998, while attempting to install a utility pole support anchor in a city sidewalk in St. Cloud, Minnesota, a communications network installation crew struck and ruptured an underground, 1-inch-diameter, high-pressure plastic gas service pipeline, thereby precipitating a natural gas leak. About 39 minutes later, while utility workers and emergency response personnel were taking preliminary precautions and assessing the situation, 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. Damage assessments estimated property losses at $399,000.
The National Transportation Safety Board determines that the probable cause of this accident was the lack of adequate procedures by Cable Contructors, Inc., to prevent damage to nearby utilities when its anchor installation crews encountered unusual conditions such as striking an underground obstacle. Contributing to the severity of the accident was the delay by Cable Contructors, Inc., in notifying the proper authorities.
The major safety issues identified in this investigation are the adequacy of the safety and emergency procedures used by Cable Constructors, Inc., crews when working in the vicinity of underground facilities and the adequacy of St. Cloud Fire Department procedures and training for responding to natural gas leaks.
As a result of its investigation of this accident, the Safety Board makes safety recommendations to the Research and Special Programs Administration, the Occupational Safety and Health Administration, the Associated General Contractors of America, the National Utility Contractors Association, the Power and Communications Contractors Association, the National Cable Television Association, the American Public Works Association, and the International Association of Fire Chiefs.
As a result of its investigation, the National Transportation Safety Board makes the following safety recommendations:
To the Research and Special Programs Administration:
Through the mechanism of the Path Forward initiative, take the lead in promulgating an industry "best practice" that advises excavators to notify the pipeline operator immediately if their work damages a pipeline and to call 911 or other local emergency response number immediately if the damage results in a release of natural gas or other hazardous substance or potentially endangers life, health, or property. (P-00-1)
To the Occupational Safety and Health Administration:
Require excavators to notify the pipeline operator immediately if their work damages a pipeline and to call 911 or other local emergency response number immediately if the damage results in a release of natural gas or other hazardous substance or potentially endangers life, health, or property. (P-00-2)
To the Associated General Contractors of America: (P-00-3 and -4)
To the National Utility Contractors Association: (P-00-5 and -6)
To the Power and Communications Contractors Association: (P-00-7 and -8)
To the American Public Works Association: (P-00-9 and -10)
To the National Cable Television Association: (P-00-11 and -12)
Inform your membership of the circumstances surrounding the December 11, 1998, accident in St. Cloud, Minnesota, to make them aware of the dangers of damage to an underground utility and the need to immediately call 911 or other appropriate local emergency response number when a natural gas leak or other hazardous condition occurs and to immediately notify utility companies when an underground facility has been damaged. Advise your membership to review and revise their anchor installation procedures as necessary to ensure that safety margins around buried utilities are absolutely observed not only above ground but throughout the installation process.
To the International Association of Fire Chiefs:
Inform your membership of the circumstances surrounding the December 11, 1998, accident in St. Cloud, Minnesota, to make them aware of the potential dangers of gas migrating into buildings from damaged underground gas lines. Advise your membership of the need to determine the hazards posed by natural gas leaks and the value of having an evacuation plan in place to be used when the situation warrants. (P-00-13)
The following previously issued safety recommendations are classified in this report:
To the Research and Special Programs Administration:
Initiate and periodically conduct, in conjunction with the American Public Works Association, detailed and comprehensive reviews and evaluations of existing State excavation damage prevention programs and recommend changes and improvements, where warranted, such as full participation, administrative enforcement of the program, pre-marking requirements, and training requirements for all personnel involved in excavation activity. (P-97-15)
Safety Recommendation P-97-15 (previously classified "Open-Acceptable Response") is again classified "Open-Acceptable Response" in the "Excavation Damage Prevention" section of this report.
To the State of Minnesota:
Require gas distribution operators to install excess flow valves in all new or renewed gas service lines, when operating conditions are compatible with commercially available valves, including service lines supplying schools, churches, and other places of public assembly. (P-96-3)
Safety Recommendation P-96-3 (previously classified "Open-Await Response") is classified "Open-Unacceptable Action" in the "Excess Flow Valves" section of this report.