Hawk Falls Bridge Replacement

Spanning the Mud Run gorge in Pennsylvania’s Hickory Run State Park, the Hawk Falls Bridge carries a critical section of the Pennsylvania Turnpike’s Northeast Extension. The original bridge, also designed by Modjeski and Masters, was a three-span deck truss that had reached the end of its service life. Following an extensive evaluation, the team found that deterioration, lack of shoulders, and the challenges of maintaining an aging, non-redundant system necessitated a replacement. 

The Pennsylvania Turnpike Commission (PTC) once again turned to Modjeski and Masters to design a replacement structure that would preserve the gorge’s natural beauty, minimize long-term maintenance, and meet modern traffic demands. The new Hawk Falls Bridge is 720 feet long and features a 465-foot steel deck arch span. The bridge has three arch ribs each composed of 11 segments. Two lanes of traffic are carried by the bridge in each direction, in addition to providing full 12-foot-wide outside shoulders and 6-foot-wide median shoulders. 

Its most defining feature is the three-rib steel arch configuration. Utilizing a three-rib system of two-hinged arches maximizes clear space under the bridge, accommodates future widening, and improves load distribution.

Nearly 3,500 tons of structural steel were used, with most external components made of uncoated weathering steel. This material blends with the site’s natural color palette and offers a durable, low-maintenance solution.

Vierendeel struts between the arches, and the absence of spandrel column bracing creates a more open, graceful appearance, ensuring the bridge harmonizes with its surroundings.

In addition to the replacement of the deck truss bridges, the existing three-span bridge carrying the I-476 mainline over SR 534 is being replaced with a 120-ft. single-span, steel plate girder bridge designed by Modjeski and Masters.