text: the us/mex fence should also be underground? since many tunnels have been discovered in just the last year the need for underground fencing seems obvious.  if you don't know about this, look it up.  the cost of underground fencing was not figured in to the budget allocations so when it comes up don't be surprised.  ask yourself is it less expensive to build a fence above ground or below ground where you have to trench through lots of solid rock? as i understand it the fence will have trenching on each side.  this is primarily to prevent cars from ramming the fence, however, it will also make tunneling more difficult.  in addition there will be sensors and unmanned drone aircraft and thousands more border patrol officers. this may not catch every drug lord tunnel, since they spend a ton of money on those, but it will make it a lot more expensive for illegal immigrants to effectively tunnel.  also, to the extent illegal immigrants have to go through a tunnel, we have won.  that would mean they were slowed to bottlenecks.  in that case the flow would be nothing like the levels we have seen over the last two decades.