Alexandria will benefit financially over the long term from the relocation of 6,400 federal employees to the Mark Center, as long as traffic improvements are in place, according to a recently released cost-benefit analysis prepared by city employees.

The move will boost retail spending, increase demand for hotel and office space, and trigger redevelopment in the corridor that could lead to millions of dollars of tax revenue for the city, the report said.

Critics say the reality is much more bleak, as Alexandria may be overwhelmed by traffic once the move is completed.

The report ignores the immediate cost of a looming “traffic nightmare” for the 200,000 commuters who drive Interstate 395, said Rep. James P. Moran Jr. (D-Va.).

“The analysis presumes the currently planned transportation fixes will resolve the problem; an assumption that can’t be proven until at least 2016 when all the improvements are complete,” Moran said in a statement.

The Pentagon is spending $20 million on transportation improvements, and the state plans to build an $80 million ramp from I-395 to Seminary Road.

Transferring workers to the newly built Mark Center, which will house the Washington Headquarters Service, the Defense Department’s inspector general and other defense offices, is one of several moves that are part of Fort Belvoir’s Base Realignment and Closure, or BRAC, process. The moves are scheduled to be completed in August.

Several members of Northern Virginia’s congressional delegation and Gov. Robert F. McDonnell (R) have requested a delay in the Mark Center move to help ease traffic congestion. An inspector general’s report released in April found that the Pentagon used flawed data in its transportation plans. A study by the National Academy of Sciences in February said the BRAC moves place an undue burden on local and state governments.

City officials released the 12-page cost-benefit analysis Thursday. The Alexandria City Council requested the document about seven months ago, and members of the city’s BRAC advisory group asked for it about three years ago.

West End residents complained that the report lacks solid analysis and an explanation on why the city included the congested site at Seminary Road and I-395 on a list of viable locations for a new federal office building.

“Regrettably, the document which the city prepared appears to be far from a cost-benefit analysis and sheds little, if any, light on how the city makes decisions,” said Donald N. Buch, the Cameron Station representative on the BRAC advisory group.

The city document “doesn’t come down to a bottom line,” said Deputy City Manager Mark Jinks, who said the analysis was performed by city staff members.

“What we have is a professionally produced, serious report,” he said. “I can completely understand folks, who make different judgments on various factors, will come to different conclusions. Those conclusions would not be unreasonable.”

Because the Mark Center is a federal building, the city will not be able to collect an estimated $60 million in real estate property taxes. Instead, according to the analysis, the larger Alexandria economy will gain an unidentified amount of revenue from new employee spending on retail goods, services and housing.

“I don’t envision very many of these new employees, if you will, stopping at Starbucks on Beauregard [Avenue] in the morning or Clyde’s in the evening before they go back to Fairfax or Prince William,” said David Dexter, chairman of the BRAC advisory group. “They might stop there because traffic will be so horrendous that they bail out.”

The BRAC advisory group is scheduled to discuss the report and related issues from 7 to 9 p.m. Wednesday at Charles E. Beatley Jr. Central Library, 5005 Duke St.