Condo tower approved for Boylston Street

An artist’s depiction of the proposed Boylston Street condo building that won city approval. To the left is the One Dalton tower, which is now under construction.Weiner Ventures

The Back Bay’s “high spine” could soon get another spike.

Developers planning a 484-foot condominium tower on Boylston Street above the Massachusetts Turnpike hope to start work on the project this year, after winning a key approval from the Boston Planning & Development Agency Thursday night.

Adam Weiner of Weiner Ventures said he is aiming for a fall groundbreaking on a deck above the Pike that would support the tower, which would rise along Boylston between Massachusetts Avenue and Dalton Street. It would take a year to build the deck above the busy highway, then two more for work on the tower itself.

Weiner said he is still working through details with the Massachusetts Department of Transportation, which also must sign off on the project. If successful, it would be the first “air rights” project to build above the Pike in decades and would bring a new spire to the western edge of the city’s skyline, alongside the Prudential Center and the new One Dalton tower, which is under construction and rising higher by the week.

The new project, however, won’t be as big as originally planned. Over the last year, it has been scaled back both in height and square footage, eliminating a second shorter building that was also planned for the site. Weiner said his team was confident that the building, and its costly deck, is still economically feasible despite the smaller size.

“These air rights projects are very complicated, but they’re definitely doable,” he said.

The plan approved Thursday includes 108 condos in the 27-story tower, atop five floors of parking and storefronts along Boylston Street. Along with its pop on the skyline, it will transform what’s now a dead block of one of the city’s major thoroughfares, said Meg Mainzer-Cohen, executive director of the Back Bay Association.

“Boylston Street is our boulevard, and here we have this big open scar,” she said. “This is really going to transform that. It’s a beautiful building.”