A proposed new stadium in Southeast Washington could cost up to $174 million more than the figure that District government leaders cited in their agreement with Major League Baseball and at community meetings aimed at winning support for the deal, according to interviews and documents.

In announcing a long-sought pact with baseball officials two months ago, Mayor Anthony A. Williams (D) put the price tag of building a ballpark at South Capitol and N streets and renovating Robert F. Kennedy Memorial Stadium, for interim use, at $440 million, most of it to be financed with public funds.

But an analysis by The Washington Post -- based on interviews with city officials, internal memos and e-mail obtained under the D.C. Freedom of Information Act -- shows that the cost could rise to $614 million if the District were to undertake all the infrastructure projects that might be needed to accommodate a team playing in Washington.

Most of the additional money is the nearly $100 million it could cost to expand Metro's Navy Yard rail station and move a major Metro maintenance garage. Officials at the transit agency said the District would be expected to cover those expenses.

The D.C. Department of Transportation estimates that it would cost $13.5 million to improve streets and sidewalks and add traffic signals and signs around the ballpark, a figure that could change after the stadium design is done.

And D.C. Water and Sewer Authority consultants said that protecting or moving massive pipes could cost $5 million or more. The utility says the District would be obligated to pay those costs.

Entities Not Consulted

The Williams administration did not specifically include any cost estimates for those items in its voluminous stadium proposal. Metro officials said that no one from the mayor's planning office consulted them until late last month, even though the current stadium site was one of several possible locations that the Williams administration identified more than two years ago. WASA officials also said they have not been formally consulted.

Moreover, Metro officials said that the District has been operating under the assumption that the Navy Yard station has the same capacity as the Stadium-Armory station at RFK, even though the Navy Yard stop is considerably smaller.

Mayoral aides contend that not all this infrastructure work is necessary and that even if it is undertaken, much of the cost could be covered by contingency funds in the stadium budget or shared by the federal government and other entities.

Stephen M. Green, a special adviser to Williams on baseball and economic issues, said the way the bonds that would pay off stadium debt are structured provides a substantial cushion. Although the District estimated the cost of the stadium package at $440 million, the bonds were designed so that the level of spending could reach $500 million without the city having to make any changes in a gross-receipts tax on businesses.

But Williams's initial cost estimate for the 41,000-seat stadium has faced growing skepticism. The District's chief financial officer, Natwar M. Gandhi, released an analysis last month that said the price could rise to $530 million, largely because the city underestimated infrastructure costs.

And late last week, the office of the D.C. auditor, the investigative arm of the D.C. Council, completed an analysis of the baseball agreement and concluded that the cost could go even higher, to nearly $584 million. In her report, the auditor, Deborah K. Nichols, cited "unrealistic" infrastructure cost estimates and the likelihood that the land at the proposed site will cost more than the $65 million budgeted.

The analysis, requested by D.C. Council member Adrian M. Fenty (D-Ward 4), who vehemently opposes a publicly financed stadium, further stated that the $22 million estimate for demolition and clearing seems low given the number of properties at the site. Nichols also concluded that the figure does not include estimates for "removing or remediating environmental hazards that may be found" at the site, which has long been an industrial area.

Growing Apprehension

Concerns that the final cost could end up much higher than initially stated have alarmed civic activists, business representatives and city leaders, including D.C. Council Chairman Linda W. Cropp (D). She stunned proponents of the deal nine days ago by saying she wanted the ballpark constructed adjacent to RFK Stadium, which would cut costs by at least 20 percent, she said.

After that idea garnered little council support, Cropp blocked a vote last week on the mayor's proposal, saying she wanted more time to explore private financing options.

Jack Evans (D-Ward 2), the council's leading supporter of Williams's plan, said he does not believe that the administration intentionally underestimated the project's costs to gain public support. But Evans acknowledged that Williams should have included more funds for infrastructure, even if it was not clear that certain work would be needed.

"They tried to get a real number, but I agree that we should have built in some safeguards," Evans said. "They should have just had all that in there to avoid the perceptions and statements from people that the costs are going up."

Handling Metro Demand

Metro officials said they see two options to deal with mass transit demands resulting from baseball games: Enhance bus service or expand the Navy Yard Metrorail station while also increasing some bus operations.

P. Takis Salpeas, Metro's assistant general manager for capital projects, said that redesigning the station to add capacity would cost close to $47 million and take three years.

Salpeas contended that the District would be responsible for funding the station's expansion because local jurisdictions and the federal government -- not Metro itself -- generally pay for station construction projects.

Metro officials said the station currently handles between 3,000 and 4,000 passengers daily. The city estimates that 50 percent of fans would use Metro -- 20,500 for sold-out games -- and Metro officials said that would create bottlenecks and long delays on the way home if the Navy Yard station is not expanded.

The 600-foot-long platform at Stadium-Armory is 30 feet wide, compared to Navy Yard's 26 feet, a difference of 2,400 square feet. Because the Navy Yard platform cannot be widened, Metro would have to double the size of the mezzanine area to handle more people, Salpeas said.

Metro officials said they were puzzled by an Oct. 8 letter that the city's transportation consultant for stadium issues wrote to the District's sports facility consultant on the project. The letter, from Gorove/Slade Associates Inc., said that the Navy Yard station has the same capacity as the Stadium-Armory station and would have no problem handling the game crowd.

Gorove/Slade officials did not return calls seeking comment.

Metro also envisions installing a new staircase, elevators to accommodate the disabled and additional fare vending equipment. The Navy Yard station has seven fare gates; Stadium-Armory has 20.

But Green, the mayor's adviser, suggested that the Navy Yard station might not have to be expanded. Overflow there could be a good thing, Green argued, because it might cause some baseball fans to use the Waterfront station and walk five blocks to the stadium, patronizing the stores and restaurants the city hopes will spring up around the site.

Even if the Navy Yard station is expanded, Green said, the costs ought to be shared by the federal government, Virginia and Maryland.

Metro officials said they also may have to enhance bus service to the stadium from some or all of the stops that are within 1.4 miles. Metro provides shuttles for Washington Redskins games that are paid for by the Redskins, according to the transit agency.

The District is facing another potentially large expense in the form of money for land. The stadium site includes a 11/2- acre lot that Metro leases to park buses near a maintenance garage. If another lot could not be found nearby, both facilities probably would have to be moved, according to the transit agency. In any case, the garage is not compatible with development plans for the area, Metro officials said.

"We know that the garage cannot coexist with a brand-new stadium and the desire to create street level retail and restaurants along M Street and Half Street SE," Arthuro V. Lawson, Metro's government relations officer for the District, wrote in a Sept. 22 e-mail to city officials. Metro estimates that the value of the agency's land at the stadium site is upwards of $35 million, he wrote.

The District's transportation department said that the price of building a new bus garage would fall between $25 million and $50 million, without land costs.

Williams's aides, however, say they believe that the garage facility would not need to be relocated because Metro could find nearby space for the parking lot.

As for sidewalk, street and lighting improvements around the new ballpark, the District's transportation director, Dan Tangherlini, said the cost estimate of $13.5 million comes out to about $1.5 million per block.

"This is the average cost of reconstructing a block with high-quality streetscape, like granite, pavement treatments such as pressed concrete and Washington globe-style lighting like in Georgetown," Tangherlini said. He also said it would cost about $1.5 million to improve freeway access to parking lots.

The Water and Sewer Authority also will have to be involved in work on a new stadium because there are several sewer, drinking-water and storm pipes that run directly below the site, including one particularly large sewer line that is 11 feet 6 inches wide.

Larry Jaworski, a WASA consultant who is familiar with the pipes at the site, said that it would be extremely difficult to move them because they are near the O Street pumping station, just a block away.

Instead, he said, WASA probably would try to build a protective bridge over the pipes to shield them from the weight of the ballpark. The process could cost $3 million to $5 million, he estimated, adding that he could not know for sure until he saw architectural plans for the stadium. Moving the pipes would probably be more expensive and time-consuming, he added.

But Green said the WASA costs could be covered by some of the $21 million in contingencies built into the mayor's stadium budget.

Staff researcher Bobbye Pratt contributed to this report.