By: Lane Enterprises, Inc
Structural plate arch as a tunnel reline material was used to address safety concerns associated with falling rock fragments in a popular hiking/biking trail known as Poe Paddy.
The old tunnel was blast constructed around 1880 to an internal height of approximately 20-ft that became a hibernation locale to an Eastern Small-footed Bat population deemed an endangered species.
The reline design included the preservation of 5 to 7-ft of space below the existing tunnel ceiling to serve as a hibernation cave for the bat species.
The flowable fill reline encasement extended a minimum 1-ft above the arch as a floor to the cave, with several depressions to allow water to pool into small ponds 3 to 6-in deep for humidity control. The 307-ft curvilinear reline (radius of curvature around 745-ft) necessitated 10 horizontal elbows.
Post-construction monitoring showed comparable humidity and temperature levels were maintained, and a recent hibernacula survey indicates a significant increase in the total number of bats using the site compared to a 2014 survey.