Bolted to the oil tank

The crew of a recently completed vessel moved a settee in the
smokeroom to allow for a better seating arrangement. In
doing so, a strong smell of diesel oil was observed. On further
investigation, it became apparent that in order to secure the
settee to the deck, the shipyard workers had drilled and
tapped a bolt right through the deck of the smokeroom into
the port medium diesel oil (MDO) storage tank directly below.
Removal of the settee had allowed the smokeroom to become a
common space with the MDO storage tank. The consequences
of ignition of diesel vapour within the confines of the
smokeroom, with its obvious heat sources, are too horrible to
imagine.
Corrective actions
1. The hole was immediately plugged and secured and the
vessel reported a near miss.
2. The information was promulgated to class, the shipyard
and throughout the owner’s fleet and offices.
3. Other vessels were checked for possibility of similar
hazards.

Source: Marine Accident Reporting Scheme (MARS 200701)
By Erik Pedrosa