Dynamite blasts echoed throughout this valley as workers excavated the tunnels, using hand tools, horses, mules, and oxen to remove the freed rock. All tunnels were dug from both ends, but this tunnel was so long that workers also dug two long, deep shafts from above to help remove rock, and these shafts were later sealed with bricks. The tunnel was slow and labor intensive to build because workers struck an overhead spring that kept it wet and difficult to excavate. Its ceilings and walls still drip with water. Tunnel No. 3 was 3,810 feet long, cost $247,272 to build, or $65 per foot, and was completed in 1873 after 3 years.