That week in July where every single post hole turned into a rock fight
Honestly, a job in Boulder last summer had us hitting granite after 8 inches on every hole, and my crew spent three days straight just on the digging, which completely blew our schedule and budget.
Yeah, that "Colorado topsoil" thing @the_sean mentioned is spot on. Trying to plant anything more ambitious than grass is a whole fight with the ground. You hit that rock layer about two inches down and your shovel just stops. Makes you wonder how any of those big pine trees even manage to put down roots.