Page 66 - OHS, July/August 2020

CONSTRUCTION SAFETY
approximately 110 pounds per cubic foot and a trench wall collapse could easily involve 4 to 6 yards of soil, which could weigh as much as a large pickup truck. The average trench is 6 feet deep and by the time the collapsed soil reaches the bottom of the trench, it is travelling at 45 miles an hour. Any workers inside the trench area are now impacted by a pickup truck travelling 45 miles per hour, and the last time I checked, this does not make for a positive outcome.
“Everyone has a great plan until they get punched in the face,” is a saying that I use in every rescue class that I have taught, and I feel that it is especially appropriate when it comes to trenching emergencies due to the time-consuming and coordi- nated effort a trench collapse emergency demands. Most fire departments have limited trench rescue capabilities due to the cost, size and large quantity of the minimum emergency shoring equipment required. That’s why it is the employer who must ensure that trained trench rescuers with proper trench rescue equipment are readily available, especially if there is a potential for the presence of a hazardous atmosphere in the trench.
While it’s a good idea to notify the local fire department in advance of any trench/ excavation activity, you should not expect them to be on “stand by” while workers are actively entering a trench. Most fire depart- ments do not have the necessary special- ized training and committing resources to be on “stand by” negatively impacts their ability to respond to the everyday “911” call volume. Firefighters and first responders do what they do because they want to help people, and notifying them helps prepare them mentally, at a minimum, and it may also allow them to alert their heavy rescue team, if they are well-resourced. They will come to your aid and do all they can, but prevention is a far better “survival strategy” as you will see from typical rescue response time frames.
Anyone who is involved in trench work should understand these time frames, and perhaps reset their expectations for res- cue operations after trench collapses. I will break down how long it could take a well prepared and trained rescue team to render a collapsed trench wall safe so that rescuers may enter the trench and start the removal of soil from on top of the trapped victims:
If a Collapse Occurs
Notify “911” and hope that the local re- sponse entity is trained in trench rescue (10 mins). Then the rescue team arrives on scene and starts to formulate plan of action (15 mins):
■ Trench lip stabilization (ground pads and spoil pile removal)
■ Ladder in the trench
■ Atmospheric monitoring
■ Victim location
■ De-watering trench
■ Support utilities
■ Shutdown any hazard causing
equipment (back hoes, excavators, generators etc...)
■ Rescue equipment staging
■ Rescue team competent person performs a trench pre-entry checklist
After that, a plan of action is reviewed with all members (10 mins):
■ Entry team members identified ■ Panel team members identified ■ Strut team members identified ■ Incident Commander identified ■ Safety Officer identified
Then, Trench Panels are installed in trench with rescue struts (10 mins). Res- cuers enter trench and start to remove soil entombing victim (30 mins) and the vic- tim is packaged and removed from trench (10 mins).
Total time is one hour and 25 min- utes (minimum time for well-trained and equipped team).
The above timeline is for a straight trench with the average dimensions of six feet deep and four feet wide and does not take into consideration the following time- consuming conditions that can be com-
monly found in everyday trenching that can easily hinder the ability for a positive rescue outcome:
■ “L” or “T” intersecting trenches
■ Damaged sewage, water, natural gas pipelines
■ Atmospheric hazards
■ Vehicle in the trench
■ Multiple victims
■ Trenches greater than 10 feet deep ■ Undermining of structural
foundations
■ Inability to control external
surcharge forces such as runways, trains, freeways
■ Victims pinned by construction materials that fell into the trench
I hope that this article sheds some light on the rescue response requirements and the immense pressure that is placed on res- cue teams, whether trained or untrained, that is unduly assumed because of an em- ployer’s willingness to circumvent state and federal trench safety laws. Getting into a trench that has not been deemed safe by a Competent Person immediately prior to entry, or (even worse) getting into an un- protected trench is like playing Russian roulette. Don’t risk the safety of your team or local first responders by taking shortcuts with trench safety.
Tim Robson is a Chief Instructor and a Standby Rescue Services Regional Man- ager for Roco Rescue. He is a Marine Corps veteran, a former FEMA task force team manager, and a former firefighter with Al- buquerque Fire Rescue. Tim is a Certified Occupational Safety Specialist and has been teaching technical rescue for 20+ years.
60 Occupational Health & Safety | JULY/AUGUST 2020
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