PHILADELPHIA, PA – The Benesch-designed rehabilitation of the 400-foot-long interconnected tunnel structure supporting JFK Boulevard over SEPTA’s electrified double track airport lines has been named Project of the Year by the American Society of Highway Engineers (ASHE) Delaware Valley Chapter. The critical repairs to the bridge over Walnut Street Tunnel restored safe travel for both vehicle traffic above and passenger train traffic below while improving the overall appearance of the boulevard.
The project included the use of Accelerated Bridge Construction (ABC) techniques for bridge joint replacement, concrete deck repairs and critical steel repairs to remove the 15-ton load posting on the bridge. Constructed in 1955, a series of steel columns supporting the tunnel ceiling were experiencing advanced corrosion and section loss. While the existing columns at the joints were replaced due to severe deterioration, it was not feasible to replace every column. To accommodate the short construction duration, ultra-high performance concrete (UHPC) encasement was used for the first time in North America to strengthen and protect the steel columns.
“The steel structure exhibited advanced corrosion and section loss due to leakage along the deck joints as well as exposure to water,” said Benesch Project Manager Gerard Kellner. “Because UHPC is self-leveling and self-consolidating and has a low permeability, it was the preferred option for this high-moisture tunnel environment.”
The project called for the rehabilitation of the interconnected “tunnel” structure supporting the boulevard over SEPTA’s Electrified Airport Lines to extend the useful life of the structure by at least 30 years. This required balancing the needs of various stakeholders with respect to traffic, schedule and budget. Through coordination with SEPTA, a three-week rail outage was planned with substitute busing from the airport to JFK Boulevard made the project possible. The project’s schedule coincided with the statewide COVID-19 shutdown but was able to proceed under emergency authorization by the Governor. The Airport Line outage was extended to seven weeks due to low SEPTA ridership during the statewide shutdown.
The rehabilitation was integral to the $6.5B Schuylkill Yards urban revitalization initiative and one of four major projects Benesch is completing as part of this initiative.