The Allenby Barracks site is leased from Israel by the US since the late 80s, early 90s. Long process finalizing. So the site is and has been there for over two decades. Of course the palestinians claim they own it, like everything else in Israel.
If you'd like to be on or off, please FR mail me.
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Just owning the land is barely the start. The amount of regulations to actually build something must be staggering.
To start with, any excavation will be ponderous, just over having to sift everything looking for antiquities and/or human remains. Everything they find will cause weeks or more of delays.
Since local zoning laws probably don’t apply, all approvals will be from every Israeli national agency bureaucracy.
Security and vetting of everyone working on the project will have to be intense, along with site security and passive defenses against things like truck bombs.
The list just goes on and on, driving up both the cost and the timetable.