ALLENTOWN, Pa. -

Sparks are flying at another critical project in Allentown.

Crews are working on tearing down the 15th Street Bridge.

They're demolishing the original bridge as part of an $8.4-million replacement project.

The bridge closed last month.

It had been closed to northbound traffic since late 2010.

The new bridge is scheduled to be in place in about 18 months.