A68/NB-391 Bridge Replacement
The Pennsylvania Turnpike Commission retained Erdman Anthony for design management, construction project management, and inspection services for the design-build NB-391 Bridge replacement project located at milepost A68.53 on the Pennsylvania Turnpike System in Lehigh County.
The project involved the replacement of the NB-391 Bridge carrying turnpike traffic over SR 4018 (Main Street) and Trout Run on the Northeast Extension in Washington Township.
The existing three-span steel-girder/floor-beam structure was replaced with two three-span steel-plate girder bridges. Both bridges have a length of 533 feet and a vertical clearance of 87 feet, 9 inches. The new structures are supported by stub abutments on micropiles and piers on 8-foot-diameter concrete caissons bearing on bedrock. Random stone slope walls were constructed in front of the abutments to help prevent future erosion.
Roadway improvements included partial milling and full-depth reconstruction, widening to the ultimate six-lane width, significant earthwork, and a steel-pile retaining wall. The project also included the installation of rain gardens, vegetated swales, and subsurface infiltration beds.
During stage 1, traffic was maintained on the existing bridge/alignment as the outside earthwork and the outside half of the structures were completed. The four lanes of traffic were then moved to the new outside structures. The old bridge was demolished in the middle, and the inside stage was constructed.