Inspection Detail

Inspection: 315916288 - Unnerstall Contracting Co.

Inspection Information - Office: Saint Louis Area Office

Investigation Summary

On October 10, 2011, Employee #1, a foreman, was found unresponsive in a new sanitary sewer system. This portion of the system was new and had not been connected to the active sewer system. A laborer entered through a manhole to assist, believing that Employee #1 had fallen into the sewer. The laborer could not escape due to the conditions in the sewer. A third worker used a fan to blow fresh air into the sewer. The laborer was then able to escape. Employee #1 was removed later and pronounced dead of asphyxia at a hospital. Firefighters tested the atmosphere with a four-gas meter and found the oxygen level to be 19.1% after the third worker used the fan. OSHA tested the manhole the next day and the oxygen level had dropped to 16.5%. The oxygen level four days later was 7.7% and the carbon dioxide concentration was 65,000 ppm. OSHA performed additional air testing over several days and oxygen levels were as low as 7.1% and carbon dioxide concentration was as high as 98,000 ppm. The coroner's report stated that Employee #1 died from vitiated air. Soil gases from organic-rich soils likely migrated into the new portion of the sewer system.

Keywords: OXYGEN DEFICIENCY, SEWER, UNCONSCIOUSNESS, ASPHYXIATED, VAPOR, CONFINED SPACE, GAS, CARBON DIOXIDE, TOXIC FUMES, RESPIRATOR