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14203 Chemical accident in USA with natural gas (pressurized)
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General accident information
Class/Quality * * * * *
Year 1998
Summary Workers were attempting a pole into a
Sidewalk when drill skidded off and cut
Marked gas line causing release, explosion
And 18 casualties
Country USA
Location CITY
Chemicals Natural gas (pressurized)
Cause Human-failure
Fatalities/Injuries 4 / 14
Occurrences or events Collapse/Destroy, El-power-brake, Evacuation, Evacuation,
Explosion, Fire fighting/Emergency response, Groundsubsidence, Groundwork,
Ignition, Penetrate/Puncture, Penetrate/Puncture, Release,
Safety-measures, Safety-measures, Slip, Stench-emission
Full accident information 
download accident report Click here to view a document containing the full accident information

Date : 1998 1211

When construction workers were attempting to lay a fiber optic cable and to anchor a utility-pole into the sidewalk, the drill skidded off its target and cut the marked natural gas main line. Gas filled the air and nearby buildings, including a pizza restaurant - empty because it was being remodeled - within minutes. Upon arrival, gas company workers entered the restaurant, searching for a way to shut of the gas source. They also tried to get people out of the buildings. But moments later, the building exploded, killing the two gas workers and two others, including a tenant who lived upstairs in the building. Police and fire officials evacuated at least a six-block area, and the smell of natural gas hung in the air for some time. The blast leveled the rear half of the bar, hurled debris up to block away, shattered windows (of a car) and knocked out power in the area.
14 people had been treated for blast-related concerns at the city's hospital. 13, including one police officer, were treated and released.
One person was still listed as critical Saturday morning.
Two of the injured were firefighters. One of them was standby at the scene when the blast blew his helmet and injured his hand, but the rest of his protective gear saved him. Another fireman got piece of debris stuck in his right eye.
Although search and rescue crews were prepared to search all night for possible survivors, officials were confident by late Friday that all victims had been found. Search and rescue efforts began within minutes of the blast, as ambulances and paramedics rushed to the scene, and firefighters began searching, often on their hands and knees, for those buried under tons of brick wall and splintered beams.
Front-end loaders were on the scene by early afternoon Friday, scooping up piles of debris, clearing areas in which firefighters and search dogs, at the scene around 1400 hours, could look for possible survivors.
Building inspectors assessed the structural integrity of buildings in the blast area, 6 downtown buildings were destroyed and 24 buildings were damaged.
According to the city assessor, the damage assessment for the buildings destroyed by the natural gas explosion was 399000 USA dollars.

The marked location of the ruptured gas line was accurate and was therefore not a factor in this accident.
While the toxicological testing performed after this accident was not useful for determining whether alcohol or drugs had any influence on the performance of the construction company crewmembers while they were installing the anchor, the crewmembers??? actions before and after the rupture indicate that they were likely not impaired by alcohol or drugs at the time of the accident.
The construction company???s anchor installation procedures were inadequate in that they did not address steps to take under unusual circumstances (such as striking a significant underground obstacle) to ensure that buried utilities were protected during the entire installation process, including the underground portion.
Had the crew foreman or his supervisor called 911 or the utility owner immediately after the rupture, emergency responders and pipeline company personnel may have had time to fully assess the risk and to take actions that could have helped either to prevent the explosion or to avoid the resulting loss of life.
Firefighters of the local Fire Department responded quickly to the scene of the leak; however, once on the scene, the firefighters??? actions did not fully address the risk to people and property posed by the leak or reduce the consequences of a possible fire or explosion.
Had the gas line in this accident been equipped with an excess flow valve, the valve may have closed after the pipeline ruptured and the explosion may not have occurred.

Probable Cause
The NTSB determines that the probable cause of this accident was the lack of adequate procedures by the construction company, 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 the construction company, in notifying the proper authorities.

Lessons learned (recommendations)
New Recommendations
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)

Previously Issued Recommendations Classified in this Report
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.

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