>I’ve just gone through a butt load of resumes

Perhaps she said "bulk load of resumes" and you misheard it as the funnier version?

Nope, this is a common expression.

If someone's feeling especially playful, they might ask if it's a metric or imperial buttload. An imperial buttload would be loosely based on the idealized/claimed size of some prominent arse in the past, while a metric buttload implies the existence of a platinum-iridium reference derriere.

Boat load?