safety bulletin #001

TOOL-BOX TALK

EXCAVATIONS

Excavations present hazards not only to the men working in them but to persons and vehicles moving about at ground level.

In general, certain precautions are essential in excavation work. Accidents involving trenches can entail:

(a)Being buried alive by cave-ins.

(b)Persons and vehicles falling into unguarded trenches and holes.

(c)Striking and cutting electricity cables and hydrocarbon pipelines.

(d)Stagnating noxious fumes killing trench workers.

Each of these potential hazards are discussed below:

(a)Cave-ins

Collapses of earthwork occur without warning and there is no way of forecasting when they might happen.

Usually, they are due to inadequate shoring, weak shoring or no shoring at all.

All excavations deeper than Four (4) feet shall be shored, benched or sloped so that the ground is cut to a safe angle of repose.

Spoil must not be placed any closer than Two (2) feet from the edge of an excavation and must be stored in stable heaps. Heavy equipment and supplies must be kept well back from the edge to avoid the sides giving away or material falling in from the top.

(b)Persons and Vehicles falling into trenches

Whether trenches and holes are deep or shallow, they must be provided with proper barriers to prevent people or vehicles falling into them.

Barriers must be solid enough to prevent a person from accidentally stumbling and falling in. Ropes can only be considered adequate when they are far enough away from the edge to act as a warning that an excavation is there.

Under some conditions, a watchman may be required.

Flashing warning lamps must be supplied at night to mark the limits of excavations.

(c)Buried cables and pipelines

If power cables or hydrocarbon pipelines are cut or breached, serious accidents can take place.

Broken telephone lines disrupt communications.

Before trenching, care must be taken to locate and identify underground lines which might become damaged.

Whenever the presence of such a line is known or even suspected, mechanical excavators shall not be used. Instead, digging shall be done by hand until the lines are safely exposed.

N.B.:-Great care must taken when using Pick-Axes.

(d)Noxious Atmospheres

Trenches located within the area of a gas plant are in a position to become traps for Heavier-than-air, Asphyxiating, toxic or Flammable gases, particularly when ventilation is poor. Such trenches, especially when they are over Four (4) feet deep, are confined spaces which shall not be entered until all necessary precautions for safe entry have been taken. An entry permit is required.

Accumulations of hydrogen sulfide, nitrogen and flammable vapors can be deadly.

Exhaust gases from internal combustion engines must be discharged well above excavations. These gases contain carbon dioxide and carbon monoxide which can be lethal in trenches.

Ladder access must be provided in excavations Four (4) feet deep or more. In long trenches, no employee shall work at a distance of more than Twenty-five (25) feet from a ladder.

SBG PCM SAFETY DEPT.

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