Really Loughatorick??? You may also recall from that very misleading video, how the Chief also said that they would start the mine and then continue right under the lake. ...
I do not know about you, but I never would not work in an open pit mine with a lake over top of me.
I'm guessing that you realize that open pit mines tend to be somewhat cone shaped, The deeper the mine, logically the smaller the base becomes.
There is a reason that Raven Trust took down the video and the reason I suspect is that the info provided was not accurate