Yes, copper would be indicative of electronic engineering, especially if there is a grid underground.
Having a bit of synthesis(*) going on, i just read this on the Thunderbolts forum by poster Jarvamundo:
"so why would Dollard fight so hard to 'save' the Marconi station? Well me thinks it's not just the aerials and poles, rather it's the giant labyrinth of copper not only under the mountain, but also installed under the sea offshore by the RCA/Navy back in the day..."
Dollard is Eric Dollard / [ericpdollard.com]
And can a pyramid have electric potential? Just by its form alone > [milesmathis.com]
And look at some of the images from the Marconi station, back in the day it was an inverted pyramid!
(*) I am not sure about the term, there could be a different word for it but i forgot, things coming together, like an Eureka moment.