The National Association of College Stores is bringing 10,000 people to Baltimore for six days in 1997.
The American Veterinary Medical Association will arrive for five days in 1998, 7,000 strong.
The World of Window Coverings, another 10,000-member group, plans to visit in both 1997 and 1999.
To get ready for them and many other large organizations that want to meet in Baltimore, state officials are breaking ground at 11 a.m. today for a $151 million addition to the Baltimore Convention Center.
The 14-year-old center at Pratt and Sharp streets isn't large enough to accommodate such groups, officials say, but will be in 1997.
"The expansion will enable us to maintain our very healthy share of the market and increase it," said Wayne Chappell, executive director of the Baltimore Area Convention and Visitors Association. "It means that Baltimore is going to be able to become a much stronger destination."
With features such as the largest ballroom in the state and a 500-seat theater with the latest audiovisual technology, "it's going to be a great building," Mr. Chappell said. "It's going to look better, and it's going to function better."
When Baltimore's Convention Center opened in 1979, it was big enough to accommodate about 80 percent of the more than 17,000 groups around the country that hold meetings and conventions, said Gil Stotler, assistant director of tourism and promotion for the convention bureau.
But over the years that fell to around 60 percent as the size of the average convention increased. "This expansion will get us back up to 80 percent, which is where we want to be," he said.
State legislators approved a funding formula last year that calls for one-third of the construction cost to come from the city of Baltimore and two-thirds from the state.
The vote came after a strong lobbying effort by Gov. William Donald Schaefer, who made funding for the expansion one of his top priorities.
The four-level expansion was planned to enable the Convention Center to attract larger conventions and to handle more than one large event at a time.
Designers say the expanded center will be able to accommodate up to three average-size conventions simultaneously, two more than it can handle now.
The expansion will result in the creation of more than 2,100 construction jobs with a combined payroll of $67.5 million, according to the Maryland Stadium Authority, the state agency overseeing planning for the project.
Analysts have estimated that annual convention activity in Baltimore will increase by nearly 70 percent when the expansion is complete and that the increased activity will generate $30.1 million a year in hotel taxes, sales taxes, entertainment taxes and other revenues.
A study by Economic Research Associates indicates that convention-goers will spend more than twice as much in Baltimore with the expansion than they would have without it -- $342 million compared with $168 million.
Each delegate spends an average of $900 during a stay in Baltimore, which means one 10,000-delegate meeting injects about $9 million into the economy, Mr. Chappell said.
The addition will be built west and south of the existing Convention Center in a two-square-block area bounded by Pratt, Howard, Conway and Sharp streets. Festival Hall, a 52,000-square-foot facility that is part of the construction site, will remain in operation until April and then be demolished to make way for the expansion.
Exhibition space will increase from 115,000 to 300,000 square feet, and meeting room space will increase from 40,000 to 85,000 square feet.
Also planned is $9 million worth of renovations to the existing center and the construction of 20 additional loading docks and a new entrance off Conway Street.
The existing Convention Center will remain in operation throughout construction of the expansion.
Work on the expansion is scheduled for completion by September 1996. After that, meetings will be held in the new space while the 1979 building is renovated.
The project is scheduled for completion by April 1997, when the National Association of College Stores will become the first group to use the expanded center.
Architects are Cochran, Stephenson & Donkervoet of Baltimore and Loschky, Marquardt & Nesholm of Seattle. Gilbane Building Co. is the construction manager.
Among the dignitaries scheduled at the groundbreaking are Governor Schaefer; Baltimore Mayor Kurt L. Schmoke; Sen. Paul S. Sarbanes, D.-Md.; Henry G. Rosenberg Jr., chairman of the Baltimore Area Convention and Visitors Bureau; Herbert J. Belgrad, chairman of the Maryland Stadium Authority; and Bruce Hoffman, the authority's executive director.