President Trump’s aggressive bid to build a wall on the nation’s southern border faces several hurdles on the ground, including endangered species, sacred tribal native territory and the likely use of eminent domain to take privately owned land, according to border experts.

But a wall built near Yuma, Ariz., proved so successful that illegal crossings were slashed 94 percent, according to Senate testimony previewed by Secrets and expected to be given today to the Senate Homeland Security and Governmental Affairs Committee.