Midsummer 2002, two male workers age 25 and 19 were overcome by toxic sewer gas - probably hydrogen sulfide - while walking through a 600 ft (183 m) length of underground sewer pipe. The men were clearing debris from the pipe in preparation for installing a Cured-In-Place-Pipe (CIPP) liner. The sewer pipe was 15 ft (4.5 m) under ground, measured 2 ft (0.6 m) wide by 5 ft (1.5 m) high, and had 1 to 2 ft (0.3 to 0.6 m) of untreated sewage standing in it. The worksite had been inactive for about 10 days prior to the two workers entering the pipe through a manhole at the downstream end of the section. They walked toward an access pit at the upstream end of the section. Three other workers were preparing for installation of the liner when the workers walking through the duct called for help. Five co-workers attempted to rescue them and were also overcome. Emergency personnel from the local fire department responded and entered the access pit after donning air-supplied respirators. They lifted the seven workers out of the pit with the aid of a nearby mobile crane. The two workers walking in the pipe were found face down in the sewage and had drowned. Neither of them was wearing a respirator nor were several key permit-required confined space precautions followed, such as monitoring before and during the workers' entry. The other five men recovered after several days in the hospital. Recommendations based on our investigation are as follows: (1) Formal communication between the hosts of a construction or maintenance site and contractors or employers regarding hazardous conditions and comprehensive safety procedures must be established before any work is to begin. (2) Employers must ensure that all components of a comprehensive confined space entry program are communicated to all workers and enforced. (3) Employers must ensure that worksite-specific written standard operating procedures governing the selection and use of respirators are followed. (4) Like emergency responders, coworkers and others should never enter a pit to attempt a rescue without proper respiratory protection.
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