SCRANTON -- A project to replace the Harrison Avenue Bridge in Scranton means an inspection Tuesday and Wednesday of a railroad tunnel underneath it.
Newswatch 16 was invited to be with engineers as they checked out the condition of the tunnel.
For the next three years, PennDOT crews will be building the new bridge spanning Roaring Brook. This week though, crews will be far underneath the bridge. There's a 110-year-old railroad tunnel underground that needs to be inspected before any more heavy equipment can be brought it in.
Before PennDOT begins Scranton's latest architectural feat, it needs to check on one directly beneath it. It probably was quite a feat to make the tunnel near Laurel Lane Drive for Scranton's electric trolley line back in 1905.
In 2015, structural engineers hired by PennDOT hope it's just as strong as it was then.
"What we're doing now is we're doing an inspection of the tunnel prior to us doing any work to make sure there aren't any flaws or anything, structural or otherwise, that we need to be concerned about during construction," said PennDOT project manager Pat McCabe.
When PennDOT starts building a new Harrison Avenue Bridge above the tunnel, it will use seismic meters to detect any vibrations here in the tunnel. For now though, the inspection isn't quite as scientific. It requires a good ear.
Structural engineers tapped the roof of the tunnel with hammers.
"Basically, you want to hear a good ringing sound, indicating that the concrete or rock they`re sounding is solid. If you hear a dead or hollow sound that`s something that you would be a little bit concerned about," McCabe said.
This tunnel is still used by The Electric City Trolley Museum in Scranton. Patrons can take a sightseeing tour on an electric trolley car and pretty soon one of the things they`ll be able to see is the construction of a brand new Harrison Avenue Bridge.
"I think it actually will be pretty interesting, people will get a chance to see the new structure as they come through," said trolley operator Jim Kosydar.
Kosydar said he will still take trolley trips for the museum while the construction is going on up above. The bridge project will replace a 90-year-old span. The tunnel underneath will be 113 by the time the new bridge is finished.
"This is huge, especially for our tourism industry. The people who ride through here absolutely love the ride and this is the biggest feature of our ride, going through a mile-long tunnel under south Scranton," Kosydar added.
PennDOT officials said the tunnel inspection will wrap up Wednesday and they do not anticipate running into any problems. The tunnel was reinforced back in 2001 when it was reopened to be used for museum trips.