Developer Monument Realty LLC said yesterday that it now controls nearly half of an eight-acre parcel that it needs to build a major office, residential and retail complex near the site of a proposed baseball stadium in Southeast, after acquiring a small lot near South Capitol and N streets SE.

Monument said it recently bought one-third of an acre from SBS Associates, run by Richard Bell of the District, for $5 million. That means it paid roughly $55 per buildable square foot for the land -- more than double what it was worth just a few years ago.

Monument has a contract to purchase two other small lots nearby from the trust of George J. Quinn and Michelle Becker and expects to close in the fall, said F. Russell Hines, senior vice president.

"We now have assembled enough land to build at least 700,000 square feet," Hines said. "This area is adjacent to the baseball stadium, and I think that will trigger a lot of interest. It's going to be at the center of everything."

More than one developer is casting a covetous eye on the neighborhood.

John E. "Chip" Akridge III, chair of the John Akridge Cos., said he is also seeking land there, though he declined to be specific because he said he is under a confidentiality agreement with the owners.

"I've got my hands on stuff there," he said. "We are active in that area around the stadium. We're pursuing several deals.

"It's the new sandbox where everybody wants to play," said Akridge, who helped build Gallery Place downtown. "It's where the next big wave of development is going to happen. The stadium is a blight buster."

Monument's land is bordered by N Street SE to the south, M Street SE to the north, and South Capitol and First streets SE on the west and east, respectively.

The company said it expects to time construction to the stadium, which is expected to be done in March 2008.

"We don't want to have a building completed if there's massive construction going on next to it at the stadium," said Hines, whose company recently bought the Watergate Hotel and plans to convert it into luxury co-op units.

Other parcels near Monument's land are owned by the Washington Metropolitan Area Transit Authority -- and two small developers who have told potential buyers that they plan to build an office building on the site, according to brokers.

WMATA uses its three acres for parking lots and bus repair. It had asked developers for proposals for the site earlier this year but withdrew the offer in May after city planners asked for a delay until a master plan for the ballpark and 35 surrounding acres could be put together. That plan is now due by the end of summer, according to city planners.