The tunnel is about 25 feet long with a ceiling height of 3 feet at the entrance and 4 feet about half way through.  The chamber is about 5-1/2 feet wide and 7 feet long with a ceiling height of about 7 feet. 

Based on the previous hillside grade, the original tunnel could have been about 50 feet long with about 25 feet being bulldozed away when they excavated for the oil well.