Complex sentence: The restoration was supervised by the Pennsylvania Department of Transportation (PennDOT), which owns and maintains the bridge, and involved minor work on the "steel floor beams and stringers", which had been added years before.
Split into simpler sentences: The restoration was supervised by the Pennsylvania Department of Transportation (PennDOT), which owns and maintains the bridge. The repair involved minor work on the "steel floor beams and stringers", which had been added years before.