I am 120% behind a wall and boots on the ground, shoulder to shoulder, fully armed soldiers with live bullets and orderer to shoot. But the tunnels do appear to be something of a problem. Understand that they are very, very deep, quite sophisticated in their construction with outlets in parking lots, under bathrooms, in vacant buildings, etc. throughout the U.S. side of the border. There also does not appear to be any current technology that can locate them at that depth.
Would think that someone could come up with technology to locate them so they could be destroyed. Or we may, indeed, have to create another Grand canyon the entire length of the border. Dynamite is certainly cheap and effective and it would be a great tourist attraction.
Constant Stare...
http://articles.latimes.com/2009/nov/02/nation/na-drone-eyes2
you keep track(yes they CAN count everything) of ALL human and vehicular traffic...
spot the hot zones.
eliminate.
Lather. Rinse. Repeat.