I-81, St. Mary's Cemetery Bridges

Erdman Anthony provided preliminary engineering, final design plan reviews, and construction consultation services for the design/build replacement of dual bridges, 383 feet and 480 feet in length, carrying I-81 over Stafford Meadow Brook, a railroad, and an access road (SR 0081, Section 271) in Lackawanna County. The project development included a 2-day VE/ACTT session in which final bridge replacement scenarios were discussed among the project team, including a number of contractors, to assist in the development conceptual traffic control schemes and bridge types. 

Traffic control was a critical issue, since the bridges are located near Exit 184, a high-traffic area providing access to the City of Scranton. Maintaining four lanes of traffic required a three-phase construction scheme that first temporarily widened the existing southbound bridge to accommodate four lanes (Stage 1), then used crossovers to shift traffic onto the widened structure while the northbound bridge was replaced (Stage 2). Traffic was then shifted to the newly completed northbound structure while the existing southbound bridge was removed and replaced (Stage 3). The design team studied crossover alternatives that navigate a variety of obstacles on the bridge approaches, including rock embankment in the median, lane bifurcation of up to eight feet, and existing overhead sign structures. Other key design issues included providing contractor access during construction (given the difficult terrain) and optimizing bridge span arrangements and materials based on geological and geographic considerations. The Erdman Anthony team used low-level aerial photogrammetry with 3-D laser scanning to supplement conventional survey methods, which were inhibited by the heavy traffic and steep terrain. In addition, our team coordinated bridge design with the operations of the Lackawanna County Rail Authority, the City of Scranton, and various review agencies. The project required close coordination with the design/build team and prompt review of contractor-prepared design plans.

Project Details

Location

Scranton, PA

Owner

Pennsylvania Department of Transportation, Engineering District 4-0

Project Contact

Robert Leonard, PE
  • Robert Leonard, PE
  • 717-766-1741 x 5006
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