[njarboe]

I have not studied the whole Boulder area in detail, but as a PhD Geologist and having visited friends in Boulder that have added a basement to their house, I'd say you might have been fed some misinformation. Maybe little topsoil but lots of glacial till. They might be right about digging being expense though. Glacial till can be full of huge boulders that are hard to trench.

[crunchlibrarian]

There are a couple areas where there is tons of topsoil sure, like in South Boulder I think many houses have basements, but as soon as you get out west or north you'll see all granite. Being a geologist I'm guessing you know the wide range of formations and different geologic timeframes we have across the span of like two miles.

[gascan]

I live on glacial till, can confirm it's a huge pain to dig through, just in my own backyard. Drilling holes for anchors, I spend more time prying fist sized rocks than drilling. Which is incredibly difficult in a four foot deep, ten inch wide hole.