Zone 6A

So I just bought 12 acres of pasture last month and am planning my homestead now that I have actual land to put it on.  My question is how likely is a root cellar to be feasible in zone 6a?  Would a fully buried, 8 feet down with cement block sides, gravel floor, and a cement roof under dirt 24 inches deep be able to maintain a 45 to 55 degree temperature?  Would it get too warm to hold foods that need cool temps such as roots, apples, meats and dairy?  I plan on hanging salted meats and I hope to have a cooler with ice for the dairy in the floor.  

There are no springs, so a dairy house is out and we're not likely to have a well as we're right on a paved road and getting utilities is very easy.  I would love a spring house though!  

Congratulations on getting your land!

I vaguely recall seeing online charts and maps that give the average deep subsoil temperatures in different areas. This may be more for ground loop geothermal heating calculations, but it would be of value to you as well.