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Occupational Safety and Health Administration OSHA

Accident Report Detail

Accident: 201482692 - Three Employees Overcome By Sewage Liquids And Gases

Accident: 201482692 -- Report ID: 0950622 -- Event Date: 11/11/1999
InspectionOpen DateSICEstablishment Name
12569926411/19/19991629Mountain Cascade, Inc.,

At approximately 4:00 p.m. on November 11, 1999, three employees were injured while working in a confined space. Employee #1 was the stand-by attendant for a confined space entry for Employee #2 and Employee #3. The confined space was a shaft that was 18 ft deep and 5 ft in diameter. This was used as a manhole entrance to the juncture of a newly constructed 42 in. sewer line and an existing 30 in. live sewer line. As the two sewer lines were being joined, the inflatable "flow-through" plug being used to isolate the live sewer from the new sewer, was removed from the live sewer line. This resulted in sewage liquid and gases entering the shaft. The ladder used to get into the sewer was removed to facilitate the removal of the inflatable plug to the street surface using a backhoe to lift the plug. At that time the 32 in. fan being used to provide augmented ventilation to the confined space was turned off to take readings of the air contaminant concentration. The meter being used fell into the live sewer and was not recovered. After the plug was lifted to the street, the ladder was replaced into the shaft so that Employees #2 and #3 could exit. Employee #2 experienced "breakthrough" of the organic vapor cartridge air-purifying respirator being used and he removed the respirator. Employee #2 lost consciousness while ascending the ladder and was supported by Employee #3. Employee #1 then entered the shaft without respiratory protection or ventilating air, and descended the ladder approximately 3 ft to assist in extricating Employee #2. While on the ladder, Employee #1 lost consciousness and fell off the ladder to the bottom of the shaft. A fourth employee assisted Employee #3 in getting Employee #2 to the surface, where Employee #3 also lost consciousness. Employee #4 attempted to restart the fan while employees from another employer at the site conducted CPR on Employee #2. Once the fan was restarted, Employee #4 entered the shaft, without respiratory protection, using a rope to assist Employee #1 back to the surface. Employees #1, #2 and #3 were transported by ambulance to local hospitals. Employee #1 was admitted for a period four days and placed on mechanical ventilation life support. Employee #2 was released from the emergency room, against medial advisement, after receiving respiratory therapy. Employee #3 was released after approximately 4 hours after receiving respiratory therapy. Emergency Response Personnel collected readings for oxygen, LEL, carbon monoxide, and hydrogen sulfide in the shaft using a Biosystems PHD Ultra (Serial number 09142) multi- gas meter. Readings obtained within the shaft revealed 300 ppm hydrogen sulfide without mechanical ventilation. No elevated readings were obtained when the fan was running.

Keywords: oxygen, sewer, ventilation, confined space, ppe, hydrogen sulfide, overexposure, sewage, respirator
Accident Details
End Use Proj Type Proj Cost Stories NonBldgHt Fatality
Pipeline New project or new addition $500,000 to $1,000,000

Employee Details
Employee # Inspection Age Sex Degree Nature Occupation Construction
1 125699264 Hospitalized injury Poisoning(Systemic) Construction laborers FallDist:
FallHt:
Cause: Trenching, installing pipe
FatCause: Asphyxiation/inhalation of toxic vapor
2 125699264 Non Hospitalized injury Asphyxia Construction laborers FallDist:
FallHt:
Cause: Trenching, installing pipe
FatCause: Asphyxiation/inhalation of toxic vapor
3 125699264 Non Hospitalized injury Asphyxia Construction laborers FallDist:
FallHt:
Cause: Trenching, installing pipe
FatCause: Asphyxiation/inhalation of toxic vapor

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