i keep visualizing the movie "the great escape" with steve mcqueen (awesome movie btw) ...... to get rid of the dirt that was being extracted during their tunneling, they had pockets sewn into their pant legs, which they filled with dirt, then as they were out walking around the compound, they would pull a string and empty the dirt from the pant leg pockets - then they would scuff their feet to mix the dirt into the ground ........
hmmmm ........ would take some tweaking but it could work ........