Trench size for training

[cpfdmiller]

im looking for input on the size of trench we should dig for training what im really looking for is how wide we should make the trench is there some what of a standerd out there on what a Typical trench will be. I wanted some in put on this. thanks

[ProgressiveRescue]

When we train we keep the with a little bit wider than a buckets with and go down between 10 & 12 '.

[Trackhoe71]

20ft -30 ft long x 10- 12 ft deep. Approx. 4 ft wide is what we had in our NFPA 1006 Technical Rescue Trench Technician Class.

[rescuezman]

I don’t know that you will find a standard on trench widths for training but here are a few thoughts that I have collected after doing this for over twenty years.
For Operations level (NFPA # 1006-Technician 1) training: trenches that are 2-4 feet wide and less than 8 feet deep are a pretty good bet. At depths less then 8 feet and with struts 4 feet long or less if you are using trench panels with strong-backs and pneumatic struts you will be able to maintain 4:1 safety factors without much problem. This holds true for most pneumatic struts but can change dramatically with timber shores. For Operations level training stick with 4 feet wide or less for high strength and good safety factors.
Buckets come in a variety of widths. You will find them from just a few inches wide to nearly 10 feet wide. Excavators typically handle wider buckets than backhoes. A common bucket width for a rubber tired backhoe is around 24 inches. Excavator buckets are commonly 48 inches and wider. I have responded to cave-ins with areas as narrow as 15 inches, as wide as 24 feet (excavation incidents) and everywhere in between. The extremes are where having a well trained and experienced Technician level (Technician II) team becomes important. Your technicians need to be able to understand soil forces and use tabulated data to design and install safe “rescue” shoring systems. At operations level training we shore trenches up to 8 feet wide with Paratech Gray struts. However, when training on deep trenches (15-20) I like to keep the width at 4 feet or less. Deep and wide trenches can certainly be safely shored but they typically take more equipment and time than the average training session allows.
We use Paratech Gold struts (bigger diameter) for trenches from 8-12 feet wide. When it gets wider than 12 feet we’ll often install raker shores which can be assembled and lowered into place from the lip which greatly reducing rescuer exposure time in the hole. The variable in design on these “technician” level trench scenarios is strut spacing. The struts must be able to resist the force with the proper safety factor. We use spacing that provides a minimum of 2:1 safety factors for rescues and bump it up to 4:1 on known body recoveries and trainings that include entry by rescuers. Your technicians need to experience all of these variables. They also need to have a clear understanding of how to design and install shoring systems that have proper safety ratios (system strength to soil force).
In summary, you will be safe and will meet your training objectives for operations level training with trench widths of 4 feet and less. I would vary the width (between 24-48”) of your trenches to keep the team on their toes. If you keep giving them the same size trench their ability to properly select a variety of strut components (bases, struts, extensions, fillers) will diminish.
For technician level team training things become inherently more complicated and risky. Technicians need to practice on wider, deeper and complex trenches. Your exercise designer must have a clear understanding of system strengths and soil forces to set up these advanced training sessions. Hope this helps.

[cpfdmiller]

thanks so much for your input that was a great help

[FiremanLyman]

Go drive around and pre plan. Seriously, find some work going on in your city, size up what they are digging. how deep are the trenches in your area? Residential water lines in the south are only foot or two under the ground, while up in the north they go below the frost line. Thisg like this will determine a lot of what you'll see. Go see how far down and wide the workers in your city are digging.