A new science building whose plans have caused tensions in town-gown relations over past months moved one step closer to construction Tuesday evening when the Elm City’s 30 alders all chimed “Aye.”

The Board of Alders unanimously approved a University parking plan that will allow Yale to build the Yale Science Building — six floors totaling 280,000 square feet of teaching and research space — at the current location of the soon-to-be-demolished J.W. Gibbs Laboratory on Prospect Street.

The swift approval Tuesday night, after six alders rose to give short speeches praising Yale’s plan, followed a number of meetings where Elm City residents testified for hours about concerns that the building would exacerbate traffic in the area. In May, after a great deal of such testimony had been shared, the City Plan Commission declined to pass the site plans and instead asked the Board of Alders to approve Yale’s central and science campus parking plan first — a move Yale contested as unnecessary at the time because the building was not expected to add additional traffic to the area.

“This is a great step forward,” Lauren Zucker, associate vice president for New Haven Affairs and director of University Properties, said Tuesday night after the plan was approved.

The building, which was first approved for construction in 2007 and then put on hold in 2008 because of the financial crisis, must still be approved by the City Plan Commission before it can move to construction.

In late 2014, when the University first unveiled the new plans, the project was slated to be completed by the end of 2019. But as the site plans have yet to pass through the City Plan Commission, Zucker declined to give a timeline for completion following Tuesday night’s approval.

“I don’t want to count my chickens before they’re hatched,” she said.

The Board of Alders passed Yale’s parking plan Tuesday night with amendments requiring Yale to encourage its commuters to take public transportation. The Board recommended a 50 percent subsidy of CT Transit costs for 9 months and asked the University to work with the city to improve bicycle infrastructure.

Yale has until July 2017 to implement the changes, and it must submit an update to the Board of Alders by the end of this year.

Alders testifying in favor of the plan Monday night described it as a symbol of cooperation between the University and the city.

“This is a historic agreement to address long-standing issues around cars and transit,” East Rock Alder Jessica Holmes said.

According to the New Haven Independent, union-backed alders such as Westville Alder Adam Marchand GRD ’99 had stalled construction after disagreements between Yale and its unions. Following this disruption, the University threatened to withhold $8.3 million in voluntary payments to the city, the Independent reported.

Before the meeting began, Hill Alder Dolores Colon ’91 addressed the crowd of roughly 100 to defend unions, referring to Labor Day and their history in fighting for fair wages.

“Union is not a dirty word,” Colon said.