Despite some reservations, engineers evaluating sites for the National Museum of African American History and Culture cited advantages of two spots, one near the Washington Monument and the other at Benjamin Banneker Overlook, a park on a hill above the municipal fish market.

The engineering study did not make an explicit recommendation. The Smithsonian Board of Regents and an advisory council of the African American museum discussed the 198-page Site Evaluation Study yesterday in a closed session. Their assessment of the findings is another step in the selection of a site. The regents are expected to announce their choice late next month.

The report, prepared by Plexus Scientific, an engineering firm, and architects PageSoutherlandPage, was made public yesterday.

The four sites under consideration include two on the Mall: the Washington Monument site, between Constitution Avenue and Madison Drive just west of 14th Street; and the Smithsonian's Arts and Industries Building, on the Mall near Ninth Street, next to the Hirshhorn Museum.

The other two spots, both near the Mall: the Liberty Loan Building property at 14th Street and Maine Avenue near the Tidal Basin, and Banneker Overlook, at the southern end of the L'Enfant Promenade.

Many supporters of the museum and President Bush have said the museum should be on the Mall.

The new museum would be part of the Smithsonian; officials there have estimated it would cost $300 million to $500 million. The study says costs could range from $356 million to $1.4 billion in 2006 dollars.

The building is expected to be 350,000 square feet -- roughly the size of the National Museum of the American Indian. The Monument site and Banneker Overlook offer the most space.

The advantages of the Monument site are its close proximity to the Mall and views of the White House and other attractions. The land is next to the National Museum of American History, which by could be linked to it by tunnel, the study suggested.

Its disadvantages include security risks -- the Washington Monument might be the target of a terrorist attack -- and the interruption of open space around Monument.

The empty plot was cited as a suitable location for a building by both the original 1791 L'Enfant plan for the city and 1901 McMillan plan. A building on the Monument site could cost as much as $672 million, the study found. The last major new building in the Smithsonian complex, the American Indian Museum, completed in 2004, cost $219 million.

The Banneker Overlook, at the southern tip of L'Enfant Promenade, is a 10-minute walk from the Smithsonian Castle with views of the Potomac River and Jefferson Memorial. The report said the rather steep area could handle a significant museum and would fit into the many plans to redevelop the Southwest Waterfront and its transportation improvements.

Construction on this site would require major rerouting of traffic off I-395 and a reconfiguration of nearby streets. "Current traffic patterns limit the site and pose some potential problems," the report noted.

One advantage, ironically, is the blandness of the area. "The site offers great latitude in terms of architectural and landscape expression, of all the sites under consideration, given no specific architectural context in the area," the report said.

Its proximity to the fish market is addressed head-on. "The nearby fish market southwest of the site can have a negative impact on the air quality of the site, depending on wind direction and air temperature," the report said.

Because of the complexity of the site and roads that would have to be rerouted, building at Banneker Overlook would cost as much as $1.4 billion. A minimal building could be done for $356 million.

The Liberty Loan site, four blocks south of the Mall, is occupied by a government building put up as a "temporary" structure in 1918 for a World War I bond drive and has a tunnel underneath for a ramp to I-395. An access ramp from Maine Avenue to 14th Street runs through the building. The site is a short walk from the Washington Monument, Tidal Basin and Holocaust Memorial Museum. The existing structure, now used by the Treasury Department, would be torn down.

Largely because of the configuration of roads on three sides, "designers would have a difficult time fitting a museum building of the projected program size on this site," the study said. The engineers also noted that it is within 300 feet of a rail line that carries hazardous chemicals, a situation now the subject of litigation.

The report said a structure with six to eight aboveground levels, facing the Tidal Basin and Jefferson Memorial, could be built but there would be no space around the museum for outdoor activities. A museum on this site could cost as much as $513 million.

The report spells out several disadvantages for the Arts & Industries site, home to a historic building on the Mall next to the Smithsonian Castle. The 143,000-square-foot structure, now closed to the public because of safety issues, is too small, the report said.

Tearing down and replacing it would cost $630 million. Updating the present building and modernizing its museum features would cost $530 million, a conversion that would provide "very little opportunity" for architectural expression, the report stated. Demolishing the building would almost certainly trigger a battle with preservation groups.

The museum, which was authorized by President Bush in 2003, is expected to be completed by 2015.