Using what and where do they get the heavy equipment? Back in the city where the Grateful Dead concert goers are walking down the street?
Right now there's safety in numbers and the zombies have the numbers..........
All over. Every little down has a dozen. Road crews. Etc.
And there just aren’t that many walkers outside the fence.
Get everyone together at the fence every morning and have a slaying party to thin the numbers. Have a rotating shift where it is always someone’s job to kill every walker on the fence.
It’s not like they breed; you could easily reduce local numbers and stay on top of it.