The apartment complex J. Brian O'Neill was building along the Schuylkill was just a small part of the King of Prussia developer's project pipeline.

The loss is a big setback, but O'Neill said he planned to rebuild the Stables at Millennium, which was destroyed in Wednesday's fire that spread to a neighboring apartment complex, leaving 375 people homeless.

"We're going to get going as soon as we are authorized to do so. We don't have a timetable yet; we're putting together our schedule now," he said yesterday.

Philadelphia real estate developers had no doubts that O'Neill would bounce back from the loss of the two under-construction apartment buildings.

"My instincts are that Brian O'Neill is a tough guy with a lot of staying power," Eric Blumenfeld, owner of EB Realty Management Corp., of Philadelphia, said yesterday.

The Millennium development in Conshohocken - where O'Neill was building the Stables alongside the Riverwalk apartment complex - is just one stop in a 20-year career built on salvaging abandoned industrial sites for offices, stores and residences.

O'Neill said the project along the waterfront in Conshohocken represented 5 percent or less of his overall backlog of nearly $4 billion. He estimated the loss of the Stables at $50 million to $80 million.

"It's a hit, but it's not the bigger part of his portfolio, by any means," said John Binswanger of Binswanger Corp., an international commercial real estate company in Philadelphia.

O'Neill has much bigger projects under way.

In nearby Malvern along Route 202, his company, O'Neill Properties Group L.P., is developing the former Worthington Steel site in a $420 million project.

In Sayreville, N.J., the company is trying to build 2,000 residences and 1.1 million square feet of hotel and convention center space on a 452-acre site along the Raritan River.

Two years ago, O'Neill said, he had invested $200 million in the Newport, R.I., area in private clubs on the waterfront and planned to bring that investment up to $500 million.

The key to how quickly O'Neill, who typically works with investors in development projects, can rebuild in Conshohocken is how long it takes to get an insurance settlement. Real estate experts said such fires often led to litigation that could drag on.

O'Neill was optimistic. "The insurance companies have been more than cooperative," he said. He said he did not expect to have to raise more capital to rebuild.

It is not clear what will happen at the Riverwalk at Millennium, which O'Neill sold for $87.5 million in 2006. That property is held in JPMorgan Asset Management Holdings Inc.'s flagship real estate fund on behalf of an institutional investor, said Mary Sedaret, a JPMorgan spokeswoman.

Donald W. Pulver, president of Oliver Tyrone Pulver Corp., which has built the eight Tower Bridge office buildings in Conshohocken and West Conshohocken since starting there in 1987, said the apartments were a good addition to the area.

Having nearby residences "was a very good amenity for our projects. It was good, and we certainly hope it will be rebuilt."

Contact staff writer Harold Brubaker at 215-854-4651 or hbrubaker@phillynews.com.

Inquirer real estate writer Alan J. Heavens contributed to this article.