Fire officials say the workers were on the Linden Street Bridge when the trench in which they were working collapsed, hitting them with gravel and concrete.
Assistant Fire Chief Lee Laubach says one of the workers was extricated around 10 a.m., more than an hour after the collapse. He says the worker is in serious but stable condition.
Chief Deputy Coroner Paul Zondlo says the other worker, 20-year-old Michael J. Wilson of Downingtown, was pronounced dead at the scene. An autopsy is planned for Thursday.
Crews have since recovered his body.
The workers weren't immediately identified. Laubach says they were employed by J.D. Eckman Inc., a road and bridge construction company based in Atglen, Chester County. A message left with a company official wasn't immediately returned. The company has not released the victims' names pending family notification.
Sukwon Lee owns an auto repair shop just a few dozen feet away from the scene. He says he had just opened up for business when the tragedy occurred.
"Every day they were working on that bridge - since Christmas. It's very shocking," Lee said.
Investigators from OSHA were on the scene, but there has been no word yet on if any safety regulations were violated
The Associated Press contributed to this report.