Share 'Question from David's Talk -- Worms'

During David's "Alcohol Can Be a Gas" talk here in New Zealand, he mentioned having garden pathways created as worm trenches. I've been planning on creating worm trenches, but I can't imagine how it could be done in a way that it could also serve as a pathway (getting walked upon). Could someone please point me in the right direction to get more info on this? Thanks, Jennifer