Thanks, Ross.
In my noobish fumblings, I encountered a hissing armless green guy, and as it turns out those guys are made of explosives. It damaged the rails near Forest Station. I filled in the hole he left but I don't yet know how to fix the cart track.
I started an excavation not far from there. If I've encroached on someone's territory (Jon), I'll gladly move my project elsewhere.