To "poo mine" was originally the equivilant to dumpster diving.
The current definition of poo mining is to go into abandoned houses, usually ones slated for demolition but not always, and scrounge through the contents left behind by the previous tenants for usable or sellable goods.
In the lower mainland of BC the homes are also stripped of any pipes and wires that can be sold as scrap.
A majority of poo miners are doing so to fuel addictions to speed.
I moved out of my house and while loading the last bunch of stuff into the truck, the poo miners were already waiting to go in.