When the Alexandria City Council approved the massive transformation of the old Potomac Rail Yard in 1999, it marked a milestone in development for the entire Washington region.

The 400-acre parcel that straddles Alexandria and Arlington, once the East Coast's main railroad hub, was the last major tract of undeveloped land inside the Capital Beltway. For years, residents had battled to keep the land from being overdeveloped, fighting off efforts to make it the home of a new Washington Redskins stadium or of the U.S. Patent and Trademark Office.

The plan approved by the City Council struck what many considered a grand compromise. Alexandria's portion of Potomac Yard, which stretches from the Braddock Road Metro station in Alexandria to Crystal City in Arlington, would have nearly 2 million square feet of office space along with extensive retail space, residential development and a 625-room hotel. But that would be balanced by 61 acres of parkland and several "town centers" in a series of new pedestrian-friendly neighborhoods reminiscent of Old Town or Del Ray.

More than four years later, that vision has yet to become reality. Although Arlington has started construction on a large office building next to Crystal City and is about to begin building residential units, Alexandria's section of Potomac Yard has languished for the past few years, with only one small townhouse development under construction. Now, the Alexandria site has been sold for the second time in three years, and some residents are raising questions about the intentions of the latest developers, Pulte Homes Inc. and Centex Corp. Residents fear the two companies want to change the plan, possibly making the project too dense with development and jeopardizing the open space and other amenities.

"They're opening up a big can of worms, because if you make changes, then everything is back on the table," said Poul Hertel, former president of the Northeast Citizens Association, which represents a neighborhood that abuts the southern end of Potomac Yard. "The stakes are extremely high here because we need to make sure this is a very livable community that fits within the fabric of Alexandria."

Others are questioning whether Bloomfield Hills, Mich.-based Pulte, which has taken the lead in negotiations with the city, is fully committed to what city officials call the sophisticated "new urbanist" style of design envisioned for the development.

"Some people think that Pulte is basically a cookie-cutter townhouse developer. There's a sense out there that they don't do the best possible job," said Bill Hendrickson, chair of the Potomac Yard Design Advisory Committee, which helps ensure that design standards are met.

City officials confirm that before the two companies purchased Potomac Yard for $105 million in late June, Pulte presented a preliminary design that was substantially different from the plan approved in 1999. Eileen Fogarty, Alexandria's director of planning and zoning, said the design was "more traditionally suburban" than the city wanted and failed to integrate the residential, retail and commercial components into "an urban village type of plan."

"The city has been very clear that we expect a very high-quality project and that there has been a tremendous amount of work by the community on this, and we expect them to comply with the existing plan," Fogarty said.

Since the city's critique, Fogarty said Pulte has submitted a revised plan that she said is much closer to what officials and the community want. She praised Pulte's enthusiasm for charging forward, saying the company is offering to do millions of dollars in initial infrastructure work the city would have had to do.

"We're very excited about this project," said Fogarty, who could not provide an estimate of the project's total projected cost.

Steve Coniglio, director of acquisitions for Pulte's Washington region, vowed to respect the wishes of both the city and the neighbors and said the development will eventually "have a Del Ray kind of look, but a bit more eclectic."

"This will not look like Centreville," he said, he said referring to the Fairfax County community. "I consider this to be one of my flagship projects. This is going to be a special place."

Asked why Pulte's initial proposal differed so substantially from the existing plan, Coniglio called it "kind of a first blush" meant only to gauge the city's initial reaction. He noted that Pulte and Dallas-based Centex are both among the nation's top five homebuilders and that Pulte recently won a major national award for quality in homebuilding.

"This isn't our first urban project," he said. "We've done this before and we're actually pretty good at it. You build what is acceptable where you build it. I would not build this project in the middle of West Virginia because it wouldn't fit."

City officials said they expect work to begin soon on infrastructure work related to the project. That work will include straightening Route 1 at the site of the Monroe Avenue Bridge, where the road makes two 90-degree turns and is considered unsafe; constructing several new roads; and various other improvements to Route 1.

To build the office, retail and residential portions, Pulte and Centex need to obtain five special-use permits from the city. Fogarty said the process will begin with community meetings over the next several months, at which residents will be asked to assess Pulte's revised plans for the site.

"How much in compliance are they? Is this the quality we want? Is there enough open space? Those will be the details we will examine," Fogarty said. "We want to get community input as quickly as possible."

It is unclear when actual construction will begin. City officials estimate that it will take at least seven to 10 years for the project to be completed. When it is, under the current plan, the Alexandria portion would have about 1.9 million square feet of office space, 735,000 square feet of retail space and 2,200 residential units, which will be a mix of townhouses and multifamily apartment buildings and condominiums.

The vision is what city officials call a "new urbanist community." Several different neighborhoods would be created, each with enough retail that people could walk to do their shopping. There will be an actual "Main Street" and a town center designed to be a gathering place.

"The idea is to echo some of the development that exists in Old Town and Del Ray, only re-created for the 21st century," Hendrickson said. "A fairly dense community, but one that brings people together and is architecturally distinctive."

The debate over what to do with Potomac Yard dates back to the early 1990s. For decades, when it was a rail yard where freight cars were sorted and sent on to their destinations, the land belonged to RF&P, formerly the Richmond, Fredericksburg & Potomac Co.

In 1991, the Virginia Retirement System bought a controlling interest in the yard, then sold it in 1996 for an estimated $570 million to Lazard Freres & Co., which at the time owned Commonwealth Atlantic Properties, the developer when the City Council approved the Potomac Yard plan in 1999.

The council's approval of a master plan amendment, a zoning change, an overall concept plan and a transportation management plan capped a long and heated debate over the site. The approved plan calls for roughly 10 million square feet of development; the community had rejected earlier visions that called for as much as 16 million square feet.

At that council meeting, about a dozen of the 70 speakers spoke out against the project, expressing concerns that it would create traffic congestion and an unsightly density of townhouses. Residents today say the congestion is already there, courtesy of the Potomac Yard Retail Center, an enormous strip mall that opened along Route 1 in 1997 and includes a Target, Shoppers Food Warehouse, Staples, multiplex theater and other retail businesses.

The Arlington portion of the new development begins just north of the shopping center, while the Alexandria section starts just south of the Target. Today, the Alexandria end consists mostly of empty fields, a few warehouses and heaps of dirt.

Many citizens at the 1999 council meeting praised the developer for what they called its extraordinary efforts to solicit public comment. But Commonwealth sold the land in 2001 to Crescent Resources LLC. Since then, residents and city officials agree, not much has been done on the Alexandria side, other than some infrastructure work.

A few months ago, Crescent sold the Alexandria portion to Pulte and Centex. A Crescent spokesman did not return several telephone calls seeking comment.

"I think Crescent was reluctant to move ahead because of the major investment they would have had to make in infrastructure before they could develop it," Hendrickson said. "I think they just looked at the capital outlay and decided it would be better to sell it."

For now, Hendrickson said he is cautiously optimistic about the new developers. Others in the nearby neighborhoods, while wary, feel the same way.

"There is a little apprehension. We have a new player and one with a questionable reputation," said Justin Wilson, president of the Del Ray Citizens Association.

"On the other hand, we're very happy to see things moving along," Wilson said. "A lot of people are concerned about this and we will be watching it closely.''

The Alexandria portion of the old Potomac Rail Yard is virtually empty as plans for a development featuring office, retail and residential space remain in limbo. City officials hope to begin the project soon.When the project is completed, the remnants of the old rail yard will be replaced by parks and several "town centers" in a series of new pedestrian-friendly neighborhoods. Officials say it could take at least seven years to complete the project.Bill Hendrickson of the Potomac Yard Design Advisory Committee said he hopes the area will resemble Old Town or Del Ray.