You describe a situation where you are doing wet blasting under wet, muddy conditions. You are having trouble with your bulk vehicles getting stuck in the mud. You are currently using a Cat D-5 tractor to pull other equipment, including the payloader that is loaded with stemming material, away from the loaded bore holes. You ask if the standard allows you to use a payloader for stemming operations and if you can use the D-5 tractor to recover the stuck payloaders within the shot perimeter. The purpose of the standard is to prevent equipment from causing unplanned detonations.
Earthmoving equipment can cause such detonations in several ways.
These include introducing an electric ignition source and causing detonation by compaction from the weight of the vehicle. The requirement of the standard does apply to work in the type of severe work environment you describe. The standard does not prohibit the use of machines, including payloaders, for loading explosives but your payloaders may not be well suited for the conditions of your operation. Operating the tractor within the vicinity of a loaded bore hole is in violation of the standard. Changes to the stemming and explosives loading pattern, reducing the number of bore holes, and use of earthmoving equipment more suitable to wet, muddy conditions would be ways of addressing the problem you describe within the constraints of the regulation.