"By the time we reach the 4900 Vein, we will have installed over 60,000 board feet of timber, and almost 5,000 feet of new ventilation duct."
A board foot is used the wrong way most times.
It is...
" The board-foot is a specialized unit of measure for the volume of lumber in theUnited States and Canada. It is the volume of a one-foot length of a board one foot wide and one inch thick."
But most people count board feet as linear feet. Which i really hope he ment
" Definition of term foot linear foot (or "lineal" foot) (ft or lf)terms used loosely to describe a one-foot length of any long, narrow object.
Occasionally the term "linear foot" is used as an alternate name for the board foot."
So giving PL the benefit of doubt we will say ment linear.
60k feet of 6 boards. Even though he used half that.
If the 2 walls were only 10 feet and ceiling was 20 feet you have 40 board feet for every 6 inches of mine
60000/40= 1500
1500/2=750 feet of tunnel was timbered
If its 2 stories worth its only 350 feet out of 7 MILES of tunnel. That is not a rehabed mine and not worth the millions spent