Sunday, February 25, 2007

Soil Collapse Conditions Illegal, Preventable

In the previous post, Don't Dig Too Deep, I wrote of the alarming extent of death and injury related to soil collapse. Historically there have been 100-300 deaths a year in the US due to soil collapse. One would hope that the current level is far lower, since these deaths are preventable, and the conditions that cause them are largely illegal to send workers into. News coverage of trench collapse is often cavalier when it reports survival, celebrating a can-do attitude and sidestepping a duty to inform. News readers deserve to be told how extensive the problem is, industry standards, or how they can take simple steps to avoid future injury to themselves and their loved ones.

Injuries that occur in the workplace deserve to be covered in the news from the point of view of compliance and employer ethics. All news coverage I have ever seen on these tragic work-related events leave off the preventable and illegal aspects of the event. The story in Georgia that prompted my post was no different.

Jordan Barab has been posting on this issue with the news media: trench collapse should not be treated this lightly; most workers do not come out alive.

Soil collapse is quiet and quick. Soil goes from supported to free fall in an instant. A collapse event initiates with little or no warning to a trench occupant. It is loudest at the end of the collapse event, yet seldom heard beyond the immediate area of the trench. Unless it is witnessed directly, or the victim can make themselves heard, a rising cloud of dust is the only evidence available to alert coworkers to respond.

A discrete soil collapse event is normally progressive in nature. First an uppermost portion of a trench wall caves off, and drops straight down like a slice off a block. When I am in a trench, even a shallow one, I am ever vigilant for this first increment. Falling from the maximum height it is moving fairly fast by the time it reaches the trench bottom. In injury events, it typically traps the feet and prevents trench egress. The collapse progresses to involve soil volumes coming from further down the wall and further back: lower velocity but far more weight and volume than the first increment. The progression commonly ends with a maximum increment.

This leaves remaining vertical wall sections unsupported at the margins of the collapse. Subsequent collapse of these vertical sections is a substantial hazard for rescue workers. 60 percent of fatalities in trench rescues involve would-be rescuers.

OSHA standards require trenches deeper than 5 feet to be shored. Shallower trenches can still be the site of fatal soil collapse, especially if workers are not standing upright. Movable temporary shoring is available within the construction industry. An alternative is to excavate sloping or terraced sidewalls. Due to vibration, heavy equipment should not be left running in proximity to occupied trenches. Interior trench corners are particularly susceptible to collapse and deserve particular caution.

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1 comment:

Philip Small said...

A follow up news story is posted
here
. It is most gratifying to see mention of an investigation into workplace safety and compliance.