Environmental Engineering Reference
In-Depth Information
DID YOU KNOW?
Here is an example of a death due to unsafe access or egress. Two employees
were laying pipe in a bench 12-feet deep, when one of the employees saw the
bottom face of the trench move. He jumped out of the way along the length of
trench; the other employee was fatally injured as the wall caved in. The walls of
the trench were not sloped, and no means of emergency egress were provided.
either operation is inherently dangerous. As a matter of fact, working around and in
excavations is one of the most dangerous jobs in construction work. It is estimated,
for example, that in the construction industry alone, cave-ins claim about 100 lives
every year; thus, excavating piping systems presents very real hazards to geother-
mal workers. Post-incident investigations of trenching and excavation mishaps have
shown that little heed was paid by excavators to the hazards involved with excavating
and trenching. Whenever geothermal construction or maintenance is conducted on
underground geothermal lines, OSHA regulations pertaining to trenching and shor-
ing must be followed. OSHA regulations for trenching and excavation can be found
in 29 CFR 1926.650-652 (Construction Standard).
An effective trenching and shoring safety program begins with knowing the haz-
ards. Workers must know what they face during these operations. Additionally, work-
ers must know how to protect themselves from injury through proper use of safe work
practices—in trenching and excavation work there is no room for error. When a trench
or excavation fails, injuries and fatalities occur fast, often in a matter of seconds. There
is no room for poor judgment in performing excavation and trenching operations.
Before beginning to trench or excavate, certain conditions must be checked. For exam-
ple, the location of utility installations, such as telephone, fuel, electric, water lines, or
any other underground installations that reasonably may be expected to be encoun-
tered during excavation work, must be determined prior to beginning an excavation.
There are other conditions that must be checked before the excavation is
attempted, such as soil, weather, and climate conditions. These factors will deter-
mine the amount and degree of sloping that must be used. Moreover, the actual
strength of trenching support members (bracing and shoring) is based on soil type
and weather conditions.
Failure to properly support walls for a trench or excavation may cause disaster.
Often, trenching and excavation jobs are driven by cost and time saving require-
ments. At other times the supervisor in charge of the operation might determine that
the trench or excavation will only be open for a short period and decides that proper
shoring is not needed. What the supervisor who takes such a short cut might end up
with is a short cut to disaster.
In auditing various excavation construction sites it is not unusual to find a weak
link in the program. This weak link can usually be attributed to a lack of supervi-
sor and worker knowledge. The auditor often finds that workers are not made aware
of the hazards involved and the precautions necessary to minimize the hazard. A
trenching and excavation training program should provide the information necessary
