A quick Google search turned up a 2001 article about a bid for the base (click here), and a conspiracy site article with more photos and info (of course, it's a conspiracy site, so take the info appropriately)...
Speculation says this site will be:
1. A forward positioning supply base for the U.S. military.
2. A major electronic surveillance post for the U.S. C.I.A. (Central Intelligence).
3. Missle silo's, associated supplies and cover.
4. All the above.
A few notes that I didn't make last time. My original picture link includes a sign (in Hebrew) listing the construction companies and managers involved. It's primarily an Arab construction team (which makes it unlikely it's for use by the Israeli army) with U.S. management.
Here's a few of the pictures, old ones and new ones (see my previous post - here - for more info also...
Note the last picture, underground entry?
Here's the full picture links I have so far:
Shiloh Pics - click here
Conspiracy Archive - click here.
Barry Chamish 1 - click here
Barry Chamish 2 - click here
Not to be overly conspiritorial, my speculation, given the formation of the 'warehouses' (no external windows) together with the stated U.S. military policy of reducing overseas bases, creating more rapid deployment forces, and pre-positioning (forward positioning) supplies, is that this is a U.S. rapid deployment forward supply base for the Middle East. Not associated in any way with the defense of Israel but rather a quick weapons and supply pickup point for U.S. forces on fast deployment to other Middle East situations.