Don't know what to use for ground cover in pen

[2 Beauts]

We have a huge pile of pine chips in our yard where the builder chipped up the trees he cut down. They've been out there about a month now, and there isn't any smell unless you're right down by the ground. We have 15 chickens, and the run is 8X18. 8X8 of the run is covered with a roof, and 10x8 is covered with netting. How often should I be cleaning it?