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14.16 Safety and Hazards Prevention 541

Figure 14.20 Picture of Trench after Cave-in.

14.16.5 Carpenter Dies When 8-ft Trench Wall Collapses during Sewer Pipe Replacement
On October 21, 2004, a 22-year-old male carpenter (victim) died when the walls of an 8-ft
(2.44-m) excavation he was working in collapsed and completely covered him (see
Fig. 14.20). A homeowner hired the victim’s employer to replace a 6-in. (150-mm) clay
tile sewer pipe leading from his home to the alley behind the home and garage. The firm
was “threading” a new 4-in. (100-mm) PVC pipe through the deteriorating existing clay 6-in.
(150-mm) pipe, and leaving the existing 6-in. (150-mm) pipe in place. Prior to the victim’s
arrival, the employer had excavated an approximately 8-ft-deep (2.4-m-deep) trench from
the home’s basement to the homeowner’s garage. Once beyond the garage the employer
dug another 8-ft (2.4-m) excavation from the garage to the alley where the sewer connection
was located. The soil conditions in the second excavation were sand/gravel and the angle of
repose (maximum permissible slope) for the excavation sides varied from 60 to 80 degrees.
To determine how far away the 4-in. (100-mm) PVC pipe was from the sewer line, the
victim either kneeled or lay down at the bottom of the excavation. The victim was still
kneeling or lying on the ground when the south side of the excavation collapsed, com-
pletely burying him and burying his coworker up to his waist. Emergency 911 was called,
and at the same time all employees jumped into the excavation to rescue the individuals in
the trench. Emergency personnel arrived within minutes, removed the victim and trans-
ported him to a local hospital where he died the next day.
The following recommendations were made:

1. Employers should ensure when employees are working in excavations that require
a supporting system that a supporting system is implemented. The excavation was
not cut to the proper angle of repose, and no shoring or trench box was used to pre-
vent employee engulfment.
2. Employers should ensure that a qualified person inspects the excavation, adjacent
areas, and supporting systems on an ongoing basis and that the qualified person takes
the appropriate measures necessary to protect workers. There was only 6 ft (1.83 m)
of room between the work area and the adjacent property line, making it difficult to
cut the trench to the proper angle of repose for the soil conditions (see Fig. 14.21).