The Vault and other wonders of Minitex

Friday, I spent an enjoyable afternoon at the UM Twin Cities Campus. Though I was very nervous and there for a job interview, the staff was so welcoming and relaxed that I almost felt like it was a visit with new friends.
One major highlight was a visit to the Vaults! I had heard about an enormous underground cavern (about a mile underground) with ceilings more than 20 feet high that seemed to go on for miles. Well, the real caverns are about 80 feet underground, and huge, but I'm not sure about going on for miles. In many ways, the truth is far more impressive than the stories. Most of the complex is double walled. The outer wall is the sandstone and shale of the cliffs lined with concave shaped, poured concrete sections that are 22 feet tall. My guess is that they behave similarly to an arch, which you may know is structurally very strong. To preserve the integrity of the ceilings, they had to place long iron "bolts," every couple of feet, through all the levels of sandstone and shale, then secure the bolts with a kind of washer and nut - this is a simplistic explanation, but I pictured something like rebar in cement but with big washer/nuts on the ends. The entire ceiling is covered with metal mesh, as safety precaution, so one can not see the washer and bolts.
The inner walls are nearly as tall and lined with poured cement sections, and a separate ceiling. This inner structure is completed watertight. There is a space of about 5' between the outer and inner walls that serves as insulation. I got to see this through a cool window in a section of inner wall. Through the window one could see the limestone, the concave cement sections and the way the moisture from the walls were beginning to create tiny stalactites.
The temperature and humidity is kept at a constant 62 degrees and 50% relative humidity, which is almost what is is naturally at that depth! In the areas where people work everyday, the temperature is higher, but one of the librarians who works in the archives, said that the first year they all had to wear those open finger-tip gloves and fleece jackets!
My favorite part of the tour, though, was the vaults! These enormous spaces really are the length of two football fields laid end-to-end! The ceilings really are about 20 feet tall and contain floor to ceiling shelves! I really wanted to run up and down the stacks and look at everything. I love browsing.
Anyway, the books and other items stored in the two vaults belong to the University and to public libraries from everywhere in the state. These items may be used only occasionally in the library of origin, but here, because of Minitex, they are available for use by every MN citizen with a library card!
That brings us to the next most interesting area of the tour - the Minitex circulation department. I learned that there are "1000 requests" for items every Monday (that number doesn't include the requests arriving every other day!) and that trucks, of all sizes, arrive and leave everyday to shuttle the items requested to hubs around the state where they are sorted and moved off to the individual library sites. To take advantage of this service, simply have your library card number handy and search for what you want here: MNLink
I'm sure that very few library users have any idea of the massive number of items that are moved through the system on a daily basis, and that tells me that the librarians at Minitex and around the state are doing a great job.