A $135 million proposal for the Downtown Crossing project released last week that aims to replace a portion of Route 34 with a new hub of business and commercial activity now faces an approval process that could take several months, city officials said.

After negotiating the terms of the development project for over a year, Mayor John DeStefano Jr. and real estate developer Carter Winstanley unveiled a 199-page proposal on Monday to repurpose the property at 100 College St., which will be made available after the downtown section of Route 34 is converted to a set of urban boulevards. The proposal, which follows 70 public meetings on the project, was submitted to the Board of Aldermen to begin the legislative approval process last week. City Hall spokeswoman Elizabeth Benton said the plan will need to be reviewed by the City Plan Commission and the Board’s finance and legislation committee before facing a vote by the full Board, a majority of which is necessary for the project to move forward.

“This project is transformational — we are talking about taking out a highway,” Benton said. “It will be a game changer in terms of the character and experience of the downtown area. It’s hard to determine how long the approval timetable is, but it will certainly be longer than a month.”

Under the proposal, the city, state and federal government would contribute a combined $35 million clearing and improving the 100 College St. site for real estate development. Winstanley Enterprises, Winstanley’s limited liability corporation for the project, would be awarded ownership of the land and spend an estimated $100 million building a parking garage and 10-story office tower targeting biomedical companies as tenants. City officials said the plan would not only generate new jobs and tax revenue but also reunify the downtown area and medical district now bifurcated by Route 34.

Benton said the City Plan Commission will be the first body to review the proposal, holding a public hearing on the plan as well as scrutinizing its land-use implications. The Commission will then make a recommendation to the Board of Aldermen on whether or not to approve the project and under what conditions. She added that the joint legislation and finance committee will then hold a public hearing on the plan, recommend amendments and issue either a favorable or unfavorable vote. The full Board of Aldermen will ultimately conduct two readings of the agreement, and a full Board vote on the details of the project will follow the second reading.

Benton said that the Downtown Crossing project is a major infrastructure and commercial development for the Elm City, and thus progress on the project must come “step by step.”

Mike Piscitelli, deputy economic development administrator for New Haven, said the proposal is also a “sound investment” for the city. Under the plan, the city must contribute $7 million to excavate and improve the 10 acre, 100 College St. property before further construction. The New Haven Parking Authority will also finance the project with $1.2 million, and the federal and state governments will put forward $16 million and $10.4 million, respectively. Winstanley Enterprises need only contribute $500,000 for initial site preparation and improvement under the deal.

“In most cities, the public has to be a partner making investments in site improvement because development is always more expensive in an urban environment,” said Anne Haynes, CEO of the Economic Development Corporation of New Haven.

After the site has been prepared for development and ownership changes hands, Winstanley aims to construct a parking garage and biomedical tower which city officials said could create as many as 900 jobs in the building alone and 4,000 jobs throughout New Haven.

Haynes added that for every one new biomedical job in the 100 College St. property, as many as three indirect jobs to support new city workers and potential residents could be created as well. She said the added pedestrian traffic would spur further commercial development in the downtown area.

“Everything from retail to professional services, marketing, accounting, restaurants, coffee shops and haircuts could stand to see growth,” Haynes said. “These indirect jobs are highly important for the city.”

But Piscitelli said the project means more to the Elm City that just job growth.

“The most fundamental benefit of Downtown Crossing is it solidifies New Haven’s place as a destination for the life sciences industry,” Piscitelli said. “We have a lot of component parts here, in the form of an outstanding medical school, laboratories and hospitals, and Downtown Crossing is a way to truly leverage those resources.”

Piscitelli added that the Downtown Crossing proposal would generate significant new tax revenue, but no formal estimate of the proposal’s gross tax revenue impact has been conducted yet. He said the city tax assessor will prepare a fiscal impact statement and deliver it to the Board of Aldermen during the approval process.

Despite the business growth and tax revenue increases that city officials say the Downtown Crossing proposal would bring, some have criticized the project’s biomedical focus, arguing that the building will only create jobs for workers who will likely live outside New Haven. Piscitelli said that while not all of the proposed building’s future occupants may live in the Elm City, biomedical positions are not the only new jobs that the project stands to encourage.

“This will create jobs at all levels of the career ladder — from low level jobs to jobs that require high skill and exceptional brilliance,” Piscitelli said.

New Haven is home to 39 of Connecticut’s 52 biotech firms.