Underground Installations

1
02/96

Committed to
Safety
Underground Installations Background A recent
high potential incident highlights the need to
alert personnel to the dangers of drilling or
digging on PDO installations. The incident
occurred during soil sampling in preparation for
the construction of a telecommunications tower.
A core sample was being taken using a coring rig.
A permit to work was obtained and the site was
checked for buried cables using hand tools before
the drilling started. A pilot trench was hand
dug and drilling began shortly afterwards. The
drill severed a 415 volt buried supply cable
causing loss of power to a nearby well. No
injuries were sustained by the workers. Recommenda
tions to prevent recurrence Drilling or trenching
should not begin until the job can be carried out
safely. A Permit to Work is required for all
digging. The pilot trench must be dug to the
full depth as specified in the HSE Manual Chapter
3 Section 4.1 "Excavation" and associated
documentation. This entails hand digging a pilot
trench to locate any underground services, the
use of a cable detector over the entire route and
consultation with specialists (electrical,
telecommunications, etc) and the site custodian
before work begins. Following this procedure is
a mandatory requirement on all drilling and
trenching jobs. Learning Points Drilling and
trenching requirements may seem onerous or over
the top to some workers. The stringent
requirements have been developed to safeguard
personnel or equipment from striking underground
cables, power supplies or piping. Fatalities
have occurred elsewhere due to pipeline ruptures
and electrocutions that have resulted from
striking underground hazards.