A proposed PATCO rail line along the Delaware River waterfront likely would be linked to Center City by a new Market Street trolley line, PATCO general manager Robert Box said yesterday.

The Market Street trolleys would be an eastward extension of SEPTA's existing subway-surface trolleys that run from near City Hall to West Philadelphia and beyond.

The trolley or light rail line along Columbus Boulevard would run from Penn Treaty Park in Fishtown, near the planned Sugar House casino, south to the Pier 70 shopping complex in South Philadelphia. From there, it could eventually be extended to the Navy Yard.

The Delaware River Port Authority, the parent of PATCO, has been studying for years how to extend transit service along the Philadelphia waterfront. In January 2008, the DRPA chose three alternatives to examine more thoroughly, including two that would connect to existing PATCO trains at the soon-to-reopen Franklin Square subway station at Seventh and Race streets.

But Box said yesterday that the more likely scenario was a PATCO link at Eighth Street and Market to a new Market Street trolley line from the waterfront.

"It would run on the surface [of Market Street] all the way to Broad," Box said. There, it would link with the subway-surface trolley.

The new service, which would require federal financial help, is probably at least $1 billion and eight to 10 years away, PATCO officials have said.

And it's unclear who would run the trolleys. PATCO might build the lines, and either SEPTA or PATCO could operate them.

"All that's up in the air. I don't think there are any turf issues there," Box said.

The economic development of the waterfront on both sides of the Delaware River is part of the DRPA's mission. The port authority sees a PATCO expansion in Philadelphia as a way to improve access to the waterfront and increase employment, residential, entertainment and shopping opportunities.

Rina Cutler, Philadelphia deputy mayor for transportation, said yesterday that "no final decision has been made" on a route to link a waterfront line to Center City. She said "a lot of discussion is going on . . . and we hope to have an announcement in three or four weeks."

SEPTA spokesman Richard Maloney said "SEPTA is very interested in the subject" and considers it crucial that any waterfront service "does connect to the SEPTA system."

He said the "engineering challenges and financial challenges" remain formidable.

The transit expansion plans for Philadelphia are part of the DRPA's proposals for growth in Pennsylvania and New Jersey.

In May, the DRPA and Gov. Corzine announced ambitious plans to restore commuter rail service from Glassboro to Camden, where passengers could connect to existing PATCO service to Philadelphia.

Contact staff writer Paul Nussbaum at 215-854-4587 or pnussbaum@phillynews.com.