Hey, I'm from Minnesota, and I can't say that were planning a tropical vacation any time soon. The attractions to quarry diving are many (almost every dive school in the area conducts ALL its dive in quarries):
1.) Its cheap!! If you can provide tank plus air fill, then often all you have to pay is the park entrance fee of a few bucks, if that!
2.) Local: Its close, we have quarries as close as 2 hours from our house, so it doesn't take much to get there, and its freshwater, so rinsing is not as big of an issue, making it easier on your gear. In regards to the techs you mentioned, we have quarries up to 450 ft deep so almost every level diver will find a challenge.
3.) You'd be surprised what some quarries have to offer, from very clear water and 40ft vis, to all the cool things people have dumped in them. Lake Ore-Be-Gone in northern Minnesota has cars, helicopters, a place, two mining rail cars, platforms, mining equipment, boats, and much more!
4.) You don't have to worry about surface conditions water, and more often then not, you will find easy shore access!
Like others have mentioned, its a thousand times better than no diving at all! I'm not speaking from much personal experience but I have researched the mines, looked at pictures and absolutely can't wait to dive more in them!!
Hope that clears things up a bit
