From Halopedia, the Halo wiki
The powder wagon is a vehicle used as a piece of large-equipment for mining.
Powder wagons are manufactured by Traxus Heavy Industries. They are long, low, and rest on a number of tires. A powder wagon includes an enclosed cargo box which can be loaded with assistance from a loading hatch that is also part of the vehicle. An attached hose can pump slurried explosives into boreholes. Powder wagons run on electricity and can be charged at charging stations. A green light on the wagon's control panel indicates it has a good amount of power. The use of powder wagons for mining is regulated by the UEG Mine Safety and Health Administration.
The Jenny Lynn Tantalite Mine on the Outer Colony of Meridian was home to at least one powder wagon before the Covenant glassed the moon in 2551, forcing the mine to be abandoned. Two years later, the members of the Office of Naval Intelligence unit Papa-10 jimmied the hatch of a powder wagon within the mine in a search for explosives.
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