City officials yesterday broke ground on a new, 20-story luxury rental residence on Congress Street.

Waterside Place, a 350,000 square foot mixed use project, will be adjacent to the Boston Convention and Exhibition Center, the Seaport World Trade Center and the MBTA Silver Line.

While the development will usher about 800 construction jobs and roughly 400 new residents into the growing Innovation District, many fear it will be a magnet for something else — more traffic.

Massport Acting Chief Development Officer Jim Doolin said the city has accounted for the additional traffic that comes with long-term growth, but added much of the traffic that exists in the district now will likely be driven out with higher parking prices.

“It is a comfort that the bulk of people who drive to the district won’t be driving there in the future because they will not be parking there,” Doolin said. “When you look at the South Boston waterfront peninsula, in the surface parking lots many of the people who park there today park and walk downtown because it is inexpensive parking. In the future, parking will be in garages and under buildings, and the price of parking will be considerably higher,” he said.

Doolin added that the motorists parking in those lots will be people who live and work in the new developments.

Motorist Ira Weinman works at International Place, but parks about a half-mile away in a lot off of Seaport Blvd., which, at 5:30 p.m. is often gridlocked.

“Yeah traffic is a concern, but my bigger concern is where am I going to park and not spend a boatload of money. Unless these (new) buildings have underground parking that is on the cheap, it’s going to make the cost of parking so much more money. That to me is a much bigger concern.”

Waterside Place construction is expected to be completed by the fall of 2013.