By Alex Howard.

Out with the old, in with the new.

Spectators looked on as the demolition of the old I-81 bridges over the Chenango River took place today.

It's the last part of the bridge work in phase 1 of the Prospect Mountain Construction Project.

Crews are expected to have the site cleaned up by the end of the week.

"A controlled demolition is actually much safer and much less impact on the environment," said Jack Williams, Regional Director of the Department of Transportation.

"So as you can see it went very well and we're very pleased with the results, but now the work begins."

Engineering students from Broome-Tioga Board of Cooperative Educational Services (BOCES) took advantage of the learning experience.

"I'm not quite sure how they brought them down, but I am looking into civil engineering and how bridges go up and everything, so this part of engineering really interests me," said BOCES student Briana Sokol.

The new bridges that have replaced the demolished ones have a 100-year service life.

Phase Two of the construction project will re-configure the interchange of Route 17, I-81 and Route 7 at Exit 4. It is scheduled to begin in 2016.