Page 584 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch14_500-554.qxd 8/7/10 8:56 PM Page 540

540 Chapter 14 Design of Sewer Systems
associated with collapsing trenches, or failed to correctly evaluate the hazards of
his work task.
2. Independent contractors should be aware of the increased potential for excavation
collapse due to adverse environmental factors, such as elevated levels of ground-
water. The incident described above occurred during the spring “breakup” when
large quantities of ice and snow rapidly melt. This phenomenon adds considerable
amounts of free water to soil throughout areas of similar geographic and climatic
conditions. Soils containing high percentages of silt and gravel can hold significant
amounts of groundwater.
3. Independent contractors should be knowledgeable about job safety and always
conduct a general hazard assessment prior to beginning any job or work task.
4. Emergency medical services and fire rescue personnel should be knowledgeable
about proper rescue techniques involving excavation sites and ensure that adequate
shoring equipment is on hand at all times. Fire rescue personnel made a number of
attempts to rescue the victim, but were impeded by their lack of adequate shoring
materials. The 3/8-inch plywood used proved to be insufficient for the task. Fire
rescue services should ensure that adequate trenching material is on hand at each
station where rescue personnel are housed. Also, emergency shoring devices (e.g.,
“Quick Shore”) are possible solutions for fire rescue stations. These lightweight,
narrow devices can be carried by one rescuer, and provide fast, adequate shoring in
emergency situations.

14.16.4 Contract Worker Dies While Reinstalling Sewer Line in Wyoming
A 39-year-old male plumber’s helper died from injuries incurred when an excavation
collapsed while reinstalling a sewer line at a construction site for a new home being
built. The victim was in an unshored, vertical-walled excavation replacing a sewer pipe
that had been installed nearly a week prior to the incident. While he was shoveling dirt
above the pipe to prevent future breakage, a 2- 3-ft (0.60- 0.90-m) concrete cais-
son/footer fell in the excavation along with the surrounding excavation wall, burying the
victim to his knees with dirt, striking him in the abdomen, and pinning him to the re-
maining wall of the trench.
The backhoe operator called to nearby sanitation workers to help, and they found
that the victim’s legs were pinned by the flat part of the concrete piece. Personnel at the
scene had released the victim and pulled him to the surface of the hole by the time emer-
gency services arrived. Fire rescue professionals found the victim balanced on a ground
surface area between two excavations, with his feet dangling into one of the holes. The
victim was in extreme pain, coherent, breathing well, and answering questions. His
lower legs were discolored and he complained of severe pelvic and leg pain. Emergency
personnel placed the victim on a backboard for transport 10 ft (3.0 m) to a more stable
area, where they applied oxygen and arranged for hospital transfer by ambulance. The
victim sustained severe internal injuries to the abdomen and pelvic area, and died the
following day in the hospital.
Employers may be able to minimize the potential for the occurrence of this type of in-
cident through the following precautions:
1. Shore vertical wall excavations to OSHA standards.
2. Establish quality control procedures to minimize reworks.
3. Improve hiring practices for short-time workers.