In the Far West in the 19th Century, railroad tunnels through "heavy ground" (i.e. fractured rock and glacial moraines) were usually lined with 12x12 (or larger) redwood timbers... old growth (500-2500 years old), straight grain, few if any knots, and naturally rot-resistant. It was not excessively expensive back then, when the the redwood forests were "practically unlimited".

Those days are long gone. Very little old-growth redwood forest remains. Salvaged large old-growth redwood timers cost $10-$12 per board foot (1 board foot = 1" x 12" x 12")(https://www.oldgrowthtimbers.com/Price_Page.htm), so $120-$144 per foot of 12" x 12" timber. That works out to about $10,900,000 to replace the rotted timber inside Alpine Tunnel with historically correct old-growth redwood.

Creosoted pine is cheaper, but the cost is still huge.

- Doug Debs