[Mr. K]

I know but $20million PER MILE?

And construction engineers here?

You could EASILY start with nothing but two chain-link fences separated by 100 yards of sand.

With guards driving patrols and IR cameras to quickly respond to any footsteps in the sand...

Then you re-inforce the problem areas, which will be always changing.

[D Rider]

Two chain links will work great with constant monitoring. But monitoring is also a cost.