SteveB wrote:

....
As the other poster said, ...

Actually, the plastic is probably a much better suggestion than the
metal...and, in thinking about it a little, I'm not so much against the
"through the slab" suggestion--w/ just these two small diameter holes
the amount of water can't be that much...I was recalling a driveway in
TN on a steep slope (imagine that in E TN ) where the expansion
joints allowed a ton of water between the slabs which eroded underneath
them...but there was a lot more area for water intrusion.