[BeHoldAPaleHorse]

But my point is if we can build a concrete fence 30 feet high 60 miles long around both sides of a major highway to keep noise from the beltway out of communities, why is it such an environmental disaster to build a fence to keep possible terrorists out of America.

Because building 30-foot-high concrete walls requires something that is a wee bit scarce in the Southwestern U.S.

Care to guess what that scarce something is?

[Wonder Warthog]

"Because building 30-foot-high concrete walls requires something that is a wee bit scarce in the Southwestern U.S. Care to guess what that scarce something is?"

Not a problem---just cast the concrete panels where the water is, and bring'em in by rail and truck.

[CowboyJay]

"Because building 30-foot-high concrete walls requires something that is a wee bit scarce in the Southwestern U.S."

Certainly not limestone. There are massive formations located within reasonable proximity to the border. Not aggregate, either. The Rio Grande is plum full of it.