On some of my recent trips back to West Virginia, I have encountered wet conditions on the North Bend Rail Trail. The state of West Virginia has had some wet years lately. Of course, Appalachia is not exactly a dry climate to begin with.
When the workers were constructing the Parkersburg Branch of the B&O Railroad they surely had to contend with a substantial amount of groundwater when drilling the tunnels.
There is an area at the East portal of the Central Station Tunnel that seems to remain perpetually wet. There must be a spring or other source of water up on the hillside because every time I have gone to the tunnel there has been a small waterfall at the East portal.
On a hot summer afternoon, you will often find that there is very cold air pouring out of the tunnel. If you like the sound of waterfalls, and who doesn't, then you will find this area to be a nice place on a hot day. There has been some days when that cold air coming out of the tunnel really felt good after a hike.