Off track? A Sixers arena at 11th and Market would compromise Jefferson Station.

The debate over the 76ers’ proposed basketball arena has been cast as a binary: Bad for Chinatown. Good for Market Street. But what if the arena was damaging to both places?

When the Sixers announced plans last July to build a home at 11th and Market Streets, Philadelphia was deep into the second summer of its pandemic discontent. Center City was struggling to adjust to the new work-from-home regime and fewer commuters. The project seemed like an answer to the city’s collective prayers, a much-needed boost for SEPTA and the Fashion District shopping mall, and a way out of the doom loop of office vacancy, economic failure, and urban decline brought on by COVID-19.

Then Chinatown balked. And the neighborhood’s fight against the project has dominated the headlines ever since.

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Lost in the swelling media storm are the many ways in which the arena could affect Market Street and Jefferson Station. The Sixers and their architects at Gensler are still in the early stages of working out the enormously complex design. But the challenges of building an 18,000-seat arena on a tight urban site — one that happens to sit on top of a busy train station — are becoming increasingly evident.

Earlier this year, the Sixers submitted a concept design to SEPTA and city planners. The proposal, which was described to me in detail by several knowledgeable sources, called for sinking the arena nearly two stories below sidewalk level. The arrangement would create an experience similar to the one at Barclays Center in Brooklyn, where fans are greeted by a spectacular wide-angle view of the basketball court as they walk in the door.

But in Philadelphia, sinking the arena — or the “bowl,” as architects call it — would mean lowering the ceilings at Jefferson Station, a soaring space where soft natural light tumbles in from windows arrayed along 11th and Filbert Streets. In a sense, the Sixers’ proposal would do to Jefferson Station what Madison Square Garden did to Penn Station: Transform airy train platforms into a claustrophobic basement station.

SEPTA, to its credit, sent the Sixers back to the drawing board.

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The Sixers are now expected to return to an earlier concept, one that would put the floor of the basketball court roughly at sidewalk level. But the rejected proposal has been an eye-opener. There’s no longer any doubt that the arena will significantly compromise Jefferson Station, no matter where the bowl is located.

Of Philadelphia’s three central train stations, Jefferson — SEPTA’s second busiest — is the one that receives the least respect. Yet it is the workhorse of the region’s entire transit network, the place where it’s easy to transfer between SEPTA’s suburban trains, the Market-Frankford Line, the Ridge Avenue Spur, and PATCO.

Completed in 1984, after the construction of a mammoth rail tunnel, Jefferson Station was the capstone to a quarter-century effort to reassemble the bones of two bankrupt train companies, the Pennsylvania and Reading Railroads, into a single system. Instead of terminating on the second floor of the Reading Headhouse, SEPTA’s regional trains now glide into Jefferson’s underground station (originally called Market East), allowing rail passengers to access the Fashion District simply by taking an escalator.

Jefferson Station may be a workhorse, but it’s also a beautiful station, one of Philadelphia’s last great, government-built infrastructure projects. Designed by architect John Bower, its north wall features a colorful, Impressionist-style tile mural by David Beck and Verlin Miller that simultaneously evokes the verdant landscapes of Fairmount Park and Philadelphia’s famous flower show. When sunlight hits the glossy tiles, the entire station becomes radiant.

The station was, in large part, what drew the Sixers to the Fashion District’s three-block-long complex. The arena would replace the mall’s westernmost block, which has a large number of vacant stores. By locating the arena above the train station, Sixers fans would be able to walk straight from the trains to their seats without having to leave the building. The Sixers say they expect half their fans to take transit to the new arena, up from 20% at the Sports Complex. If that projection is correct, the Fashion District could benefit enormously.

Since the station is the linchpin of the arena project, you might think the Sixers would go out of their way to avoid messing with its three-story-high space. But because the 3.6-acre site is relatively small for an NBA arena, the Sixers are desperate to maximize every inch of the footprint.

To fit the bowl onto the site, the Sixers will almost certainly need to insert a floor above the station. That would lower the ceilings, squashing Jefferson Station down to two stories. Although the platforms would still receive some natural light from windows in the adjacent skyscraper (originally called One Reading Center, now Jefferson Center), the station would become as dark and warrenlike as a subway station.

Besides lowering the station ceilings, the Sixers will almost certainly have to drop additional columns onto the concourse floor to support the bowl. No one can say yet whether those columns will land on the train platforms. But we do know that the presence of structural columns is one reason Penn Station’s platforms feel like cattle chutes.

Whatever the extent of the construction, building over an active rail line isn’t for the faint of heart. Most of the work will have to take place between 11 p.m. and 5 a.m., so the electricity can be turned off in Jefferson Station. No trains would be able to run during that period. The construction is sure to have a major impact on neighboring businesses.

Jefferson Station isn’t the only public space at 11th and Market that will be affected by the Sixers project. All the streets bordering the arena will be degraded. None more so than Filbert Street.

During the creation of the shopping mall (originally, the Gallery) in the ’70s, Filbert was effectively reduced to a service street and lined with parking garages. A Greyhound bus terminal opened on Filbert in 1985, directly behind Jefferson Station.

Since the 11th Street portion of the mall isn’t big enough for an NBA-approved arena, the Sixers plan to purchase the Greyhound property. But they will need to span over Filbert Street to unite the two parcels.

Initially, it was thought that Filbert would remain open to cars. But the Sixers now want to close the block between 10th and 11th Streets. That stretch would become a publicly accessible corridor within the arena, lined with sports-themed restaurants, bars, and shops.

Such a closure means the city would have to reorganize the traffic pattern around the mall. The changes could actually reduce congestion from the arena by forcing drivers to approach the Filbert garages from different directions. The Sixers are also hoping to institute a system requiring fans to reserve parking spaces in advance, thus reducing the amount of time drivers spend cruising city streets.

Still, the downsides can’t be ignored. Closing Filbert Street would create yet another underpass in an area already chockablock with dark, tunneled-over streets. And it effectively privatizes a piece of the city’s street grid. How will the city respond if the Sixers ask to install gates at either end of the corridor?

The Sixers argue that the arena will be a catalyst for reviving retail along Market Street, and their plans call for activating the arena’s ground floor with shops and restaurants.

Living up to that promise won’t be easy. Built in the ‘70s, the mall was infamous for long blank facades that gave it a fortresslike appearance. So much of the exterior was claimed by emergency exits and ventilation systems that there was little frontage left over for anything else. It took a heroic renovation, completed in 2019, to pry open the facade and make room for street-facing stores.

Unfortunately, some of that newly opened street frontage will have to be taken back to make room for the arena’s entrances. To ensure crowds can exit quickly in an emergency, the Sixers architects may also have to add more exit doors around the perimeter. In the end, there may be enough frontage for only one or two retail spaces on Market Street.

Other basketball arenas, such as Barclays and Boston’s TD Bank Center, occupy similarly tight urban sites. But neither had to contend with the level of complexity that the Sixers face. Think of the Fashion District as a layer cake, with different strata owned by the city, SEPTA, and the mall’s owner, Macerich Co. Sorting it all out is so daunting that the city’s Department of Planning and Development is hiring an arena consultant to help assess the implications of the Sixers’ design. Even though the site has the highest zoning classification, CMX-5, it will still require variance for stadium use.

The city is especially worried that the Sixers do not have enough room for a plaza, where crowds can gather before and after games. What happens when tides of energized fans flow directly into city streets after a game? To manage the crowds, the city may have to temporarily close 10th and 11th Streets. That could cause problems for the 23 bus, which starts at 11th and Market.

Gensler, the Sixers’ main architect, is known for its sports expertise and for designing arenas like the Chase Center in San Francisco, so it may well come up with a clever solution to these challenges. The Sixers also expect to hire what’s known as a “design architect” to infuse the building’s exterior with some extra pizzazz.

But given the immense obstacles, it’s worth asking whether this is the best downtown site for a Sixers arena. While the so-called Disney hole at Eighth and Market is the wrong shape for an arena, there is no shortage of empty lots along Arch Street, all a short walk to Jefferson Station. And there’s always Broad and Pattison, which, by the way, also has excellent transit.

Where does that leave Market Street, then? The train station wasn’t renamed by accident. Jefferson Hospital has been steadily moving north from its main campus on Walnut Street. It has already established a beachhead in the former Aramark tower at 11th and Market. There’s room for two more towers on top of the Fashion District, which was designed to support an overbuild. Meanwhile, residential developers have gradually been changing Market Street’s retail character by erecting apartments.

Unlike the fans who go to basketball games, the people who live and work in such towers are present every day. They will shop in the Fashion District’s stores, eat in Chinatown’s restaurants, and use Jefferson Station’s trains. Before Philadelphia commits to an arena, it’s worth remembering that there’s more than one way to save Market Street.