No need to keep them dry.I agree with aart on few inches and keep dry. The last thing you need is moldy run for all of you.
Not necessarily.Wood chips if they don’t dry out cause mold
It's true that freshly chipped tree branches, especially if they contain lots of green leaves, can develop toxic levels of molds. That's why you spread them thin in the run and when adding take the outer layer of the pile to add more thin layers in the run.