I'm still a little confused. The concrete is for the foundation for the coop, right? How are you protection the runs? The reason I mention skirts for run protection is, from a predators point of view it's a matter of how much energy is spent to get to your goal.
So say I'm a fox and you have your fence buried 8" below ground. I come up to the edge of your run and I smell chickens. I love chicken dinner. My first instinct is to a dig under the fence. So for this to happen the fox would need to dig down 8" plus the width of his body and he's in. A fox can dig a 12" hole in under an hour if it's the ground is not full of stones.
With skirts, I come up to the to your run and I smell chicken. My first instinct is to dig under the fence, but wait, there is fence under my feet. If I'm not real a clever fox I'll walk around and around the run looking for a place to dig under the fence or find some other weak point. If I'm a real clever fox and I figure out that I must move back to the edge of the wire skirt, and let say the skirt is 16" wide, I now have to dig 16" plus my body width to get into your run. Twice the effort to get in and I would need to be very clever to figure it out.