Blue Ridge Parkway tunnels

Blue Ridge Parkway tunnels consist of a total of 26 vehicle tunnels constructed along the 469 miles (755 km) of the Blue Ridge Parkway. One, the Bluff Mountain Tunnel,[1] is in Virginia and twenty-five are in North Carolina.[2]

Blue Ridge Parkway tunnels

Bluff Mountain Tunnel
Overview
Location	Blue Ridge Parkway
Route	Blue Ridge Parkway
Operation
Work begun	1930s
Constructed	stone and concrete

The design standards specified a minimum impact on the land. The vehicle tunnels were often constructed to reduce excessive landscape scarring that open cuts would have produced. They are used in areas of steep terrain where ridges run perpendicular to the roadway alignment.

North Carolina's more rugged terrain required the majority of the tunnels. Most of the work on the tunnel digging was done by hand and provided by the Civilian Conservation Corps in the 1930s.[3] Little machinery was used with the intention of creating manual labor in depressed economic times. They did have for tunneling truck-mounted water-cooled compressed air drills called "Jumbos." After the initial holes were drilled into the substrata, dynamite was used for blasting away the rock.[4]

Concrete lining was done during construction due to tunnel cave-ins.[5] This concrete lining was first used in the Devil's Courthouse Tunnel. It was later discovered that it enhanced the interior lighting within the tunnel itself. Where done the lining covered about a quarter of the interior structure. An additional benefit was the elimination of moisture entering the tunnel. Moisture in the winter caused ice problems.[6]

The Pine Mountain Tunnel is the longest on the Parkway at 1,434 feet (437 m). Ferrin Knob Tunnel #1 is the first and longest of the triplet tunnels. The local people once referred to ferns as "ferrins." Ferrin Knob Tunnel #2 is located at milepost 401.3 and Ferrin Knob Tunnel #3 is located at milepost 401.5.

The distinctive stone masonry portals now on the parkway tunnels were generally not part of the original construction of the 1930s. They were added later.[7]