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14.16 Safety and Hazards Prevention 539
2. Follow sewer plug manufacturers’ recommendations and other safety precautions
on the installation and use of inflatable sewer plugs. According to the manufac-
turer, filling the plug with water instead of air when the plug is submerged will
greatly reduce the force of a rupture.
3. Develop and implement specific confined space entry and work procedures.

14.16.3 Independent Contractor Dies in Sewer Line Excavation Engulfment, Alaska

A 34-year-old male independent contractor (victim) was killed as a result of traumatic
head and neck injuries during a sewer line excavation cave-in.
The sewer pipe leading to a private residence had parted, causing effluent to build up
around the point of the break. Sewage was also backing up into the home’s garage. The
owners of the home contracted with the victim to perform the above procedure. The victim
rented a back hoe/front-end loader from a local company to perform the trenching opera-
tion. Excavation site and soil conditions on the day of the incident were as follows:
• Approximately 2 inches (50 mm) of blacktop (driveway)
• Three and one-half feet of partially frozen, sandy/silty gravel
• Water-saturated sandy/silty gravel below the semi-frozen gravel.
The victim was repairing the sewer line at the private residence and had excavated a
12-ft-deep by 15-ft-long (3.66-m-deep by 4.57-m-long) trench with 90-degree sidewalls to
access the existing sewer line. The victim then called another contracting service to re-
move groundwater/sewage that had accumulated in the trench. After this operation was
completed, the victim entered the unshored trench via a ladder for another inspection. At
this time the walls of the trench collapsed, and concrete slabs (from a sidewalk leading to
the private residence) fell into the trench. These slabs struck the victim on the head and
neck, and caused him to fall from the ladder. He was subsequently buried by the incoming
soil from the trench walls.
Witnesses called 911 and fire rescue personnel responded. They arrived on scene and
began to attempt a rescue. The rescuers stood on the “fill” in the trench near the ladder
where they began digging with shovels in an attempt to locate the victim. Because of the
instability of the trench (rescuers had to abandon the trench on several occasions due to
collapsing soil), fire rescue personnel began looking for shoring materials. An attempt was
made to shore the walls with 3/8-inch (0.95-cm) plywood, but this proved to be unsuccess-
ful. Because of the elapsed time and the imminent and immediate danger to rescue person-
nel at the site, Department of Labor officials requested that the rescue attempt be aban-
doned and the trench be widened and sloped to a safer “angle of repose.” The victim’s
body was located under the concrete slabs approximately 3 hours after the trench collapse.
The employee was a local independent contractor who specialized in “home improve-
ments.” He operated primarily as a “jack of all trades,” and had completed jobs in carpen-
try, electrical installation, and other building trades. He had been in business for 5 years,
and worked primarily on rental properties. He was a vocational school graduate and had
served in the military. However, little is known about his specific training in trenching and
shoring. Most training he received appears to have been “on-the-job” training.
Based on the findings of the epidemiologic investigation, to prevent similar occurrences:

1. Independent contractors should be aware of the potential dangers of trenching or
other excavation operations and be knowledgeable about proper techniques of
sloping and shoring. The victim failed to use any method of trenching appropriate
for the excavation operation. He was apparently either unaware of the dangers