For trench workers, few things are as concerning as the possibility of a trench collapse. The weight of dirt and stone is far greater than many people realize — up to 3,000 pounds per cubic yard, according to Safety and Health Magazine — but workers are well aware of this danger. They know that a collapse can cause fatal injuries in mere seconds.

So, will they have any warning before this happens? They may. You can certainly see warning signs in some situations, such as water eroding the side of the trench, soil shifting under pressure or other things of this nature.

However, the National Safety Council (NSC) warns that many of these incidents happen with no warning at all. A trench can seem perfectly safe one minute and then collapse the next. Workers may have been using it for hours or even days with no problems before the collapse.

The key is not to count on the warning signs. Look for them and respect them if you see them, but understand that you may have no warning. The collapse could come out of the blue. Therefore, it’s more important to plan for safety in advance — using the right safety devices to avoid a collapse — than to wait to see if things begin to look more dangerous during the job. Conditions may not change at all until the deadly collapse, and workers can get trapped in a heartbeat.

Workers who get hurt in these collapses need to know what legal options they have. The same is true for family members who are left behind when a loved one dies on the job.