CHICAGO (CBS) — Two days before the City Council Zoning Committee votes on the massive Lincoln Yards project on the North Side, developer Sterling Bay has agreed to double the number of affordable housing units it will build on-site.

Lincoln Yards would redevelop more than 50 acres of largely industrial land along the North Branch of the Chicago River; adding housing, retail, public transit upgrades and new parks.

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Ald. Brian Hopkins (2nd) already has given his backing to the ambitious $6 billion project that would be built between Lincoln Park and Bucktown. On Tuesday, he announced developer Sterling Bay has agreed to double the number of affordable housing units it would build on site – from 300 to 600.

Rendering of a birds-eye view of the Lincoln Yards development, along the Chicago River between Bucktown and Lincoln Park. (Credit: Sterling Bay)

Overall, the project will create 6,000 new residential units. For a project that size, Sterling Bay must build 1,200 units of affordable housing, at least 25 percent of them on-site.

Sterling Bay previously committed to the bare minimum of on-site affordable housing, or 300 on-site units, but now will double that number. In addition to the 600 units it now will build on-site, it will build 300 more within 3 miles and pay $39 million to the city’s Affordable Housing Opportunity Fund.

While the project has the support of Hopkins and Mayor Rahm Emanuel, the two remaining contenders in the race for mayor have said the project is being rushed through the approval process without sufficient transparency or community input.

Mayoral candidates Lori Lightfoot and Toni Preckwinkle both have said approval of the Lincoln Yards project should be delayed until a new mayor and City Council are sworn in. Other opponents say there are too many unanswered questions about the project to move forward with taxpayer-financed assistance for Lincoln Yards.

Rendering of a proposed Chicago River lookout in Lincoln Yards. (Credit: Sterling Bay)

Hopkins, however, said the development has nothing to do with the mayoral election because it was dreamed up two years ago and officially launched eight months ago.

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The City Council Zoning Committee is scheduled to vote on the project on Thursday. After that would come a final vote by the full City Council, as soon as next week.

While the City Council traditionally gives aldermen the privilege of approving or rejecting development projects in their wards, many aldermen have voiced concerns that the Lincoln Yards project does not include enough affordable housing on site.

With that in mind, Hopkins announced Tuesday the affordable housing component of the plan would be boosted dramatically.

“We’re doubling it from 300 up to 600 units. That is one of the largest single gains in affordable housing on the North Side,” he said.

Rendering of a proposed transit center in Lincoln Yards, including a Metra station, an extension of the 606 bike trail, and one of three new water taxi stations. (Credit: Sterling Bay)

Ald. Walter Burnett (27th), who had been among the aldermen criticizing the original affordable housing plan in the project, called the change to Lincoln Yards “a great deal.”

“I’ve never seen a full 10 percent go on the North Side, and then another 5 percent to go within 3-mile radius, and another 5 percent to go to support affordable housing throughout the city of Chicago. I think this is a win-win situation,” he said.

Diane Lemas, board president of Communities United, said Sterling Bay’s agreement isn’t everything they wanted but is enough to support the project.

The new affordable housing commitment is not the first major change for the Lincoln Yards project. Sterling Bay originally proposed building a 20,000-seat soccer stadium and an entertainment district run by Live Nation, but Hopkins rejected those ideas and demanded they be replaced by park space. Sterling Bay revised its plan to eliminate the stadium and Live Nation venues.

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The sweeping project includes some 12 million square feet of new buildings, including skyscrapers as high as 500 feet. Proposed infrastructure improvements include new bridges, a new Metra station, the extension of the 606 trail, additional CTA service and new water taxi stops. It is expected to take 10 years to complete if approved.