You might want to take a look at how painful the undersea tunnel across the Bosphorus have been. Quite a well written article as well: https://www.newyorker.com/magazine/2015/08/31/the-big-dig

In short — when contract builders determine depths of tunnels based on earliest known human habitation, it’s often the case that they find humans got there earlier than thought. Then the proposed great solution to the traffic problems instead becomes an archeological dig site for the next decade.

> Same with a deep tunnel. I don't think 150m down there would be substantive archeology. I don't think anyone is willing to countenance going below the remains is viable.

Usually it's the opposite: things well buried tend to last longer.

Sort of like the joke among those building Finland's nuclear waste repository: they'd dig a mile under the bedrock to create a storage chamber for the waste, and what they'd find in the mining spoils would be... perfectly preserved, 500,000 year old copper canisters. Filled with formerly-radioactive waste.

The point is that 150 meters down would likely be older significant human inhabitation of the area.