Amtrak and its development partners want to build a new underground concourse linking 30th Street Station with SEPTA's subways and trolleys as the first step in a 35-year plan for the area.

The concourse, to be topped by a skylight and lined with shops along its 250-foot span, would be completed during the first half of the 2020s, according to a draft of the 30th Street Station District Plan to be released during an open house at the station Wednesday from 4 to 7 p.m.

The draft is the latest stage in a $5.25 million study, nearing completion after two years, of plans for the station. It comes weeks after Drexel University and Brandywine Realty Trust released plans for their Schuylkill Yards development on an adjacent section of Philadelphia's University City district.

"These two areas, their fates are intertwined and linked," project director Natalie Shieh said. "It all centers around and starts with the value that 30th Street Station creates."

The 30th Street Station District Plan is being led by Amtrak, SEPTA, Drexel, Brandywine, and the Pennsylvania Department of Transportation, which controls the Schuylkill Expressway on the project site's east.

The backers anticipate a new neighborhood with 10 million square feet of commercial and residential real estate amid parks and promenades, mostly on a cap over what are now 80 acres of rail yards.

The concourse linking the station - served by Amtrak trains and SEPTA's regional rail lines - to the subway and trolley platforms is part of the district plan's first phase, set to last until the early 2030s.

A tunnel between the two stations was shut in the 1980s because of safety concerns. Restoring the link would make it easier for those arriving at the station - especially tourists - to reach other parts of the city more easily, said John Hepp, a professor at Wilkes University in Wilkes-Barre who researches transit history.

"It would turn 30th Street Station into what it was always intended to be: a grand ceremonial gateway into Philadelphia," he said. "It could help Philadelphia development in ways not even connected to 30th Street."

Other elements of the district plan's first phase include pedestrian-friendly upgrades to the station's exterior and a new Amtrak passenger concourse in a northern section of the building now used as a valet parking lot to accommodate an expected doubling in passengers to 25 million a year by 2040, Shieh said.

The hope is that these early enhancements to and immediately around the station will make the more expensive rail yard cap more feasible by boosting area property values, she said.

"We have to make this an amenity that would make people want to live here and make businesses able to attract the workers they want here," she said.

University City seems to be on a trajectory that could eventually make the rail yard economically feasible, said Christophe Terlizzi, who heads First Niagara Bank's commercial real estate practice in the region.

Businesses and residents are already drawn to the area's educational and research institutions, such as the University of Pennsylvania, Drexel, and Children's Hospital of Philadelphia, and to the ease of transport to other East Coast cities afforded by the station, he said.

The district plan - along with Brandywine and Drexel's Schuylkill Yards project, which call for 8 million more square feet of new and redeveloped real estate - will make the area even more attractive, Terlizzi said.

"The presumption here is you're creating a critical mass and a transportation hub," he said.

The project's financial feasibility won't be considered until the final draft of the plan is released in the summer, Shieh said. In the meantime, she said, planners are putting together a detailed outline to prepare for when concrete steps can be taken.

"What we're doing is starting with the ambition first," Shieh said.

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