As many as 12,000 modular homes — along with a plant to build them — may rise on the 430-acre site of the old U.S. Steel South Works plant, the local alderman said Tuesday.

Last year, a split between the steel giant and prominent Chicago developer Dan McCaffery killed a similarly ambitious plan to build a “new city” on the long-vacant lakefront site roughly between 83rd and 92nd streets and Lake Shore Drive and the lake.

McCaffery’s plan called for building as many as 13,000 homes, 17.5 million square feet of commercial space and a marina with slips for 1,500 boats.

Now a joint venture between Barcelona Housing Systems and WELink has emerged as the winning bidder for the massive site.

Ald. Susan Sadlowski Garza (10th) said she has been working with Barcelona Housing officials, who have also met with the city’s Department of Buildings and the building trades.

“They did their due diligence, and they’ve got all of their ducks in a row. They’re gonna be building a manufacturing [plant] on the property where they’re going to be building modular homes. They’ve done it in Barcelona and Argentina. It’s a new, innovative product that’s never been here before,” Garza said.

“They can do things a lot faster because of the technology they use. South Works is gonna be used as a prototype to, hopefully, build these houses all over the Midwest.”

Chicago Federation of Labor President Jorge Ramirez said he is “always excited” about the prospect of development with potential to put hundreds of members of the building trades to work.

“I’ve just got to make sure that there’s a meeting of the minds as to how these things are gonna get done,” Ramirez said. “That they’re not cutting corners or [compromising] safety standards. They’re lifting people up into the middle-class and respecting labor. All of the run-of-the-mill standard types of concerns.”

Barcelona Housing officials could not be reached for comment. Neither could Larry Goldwasser, a senior director for Cushman & Wakefield, the real estate broker hired last year to market the property.

Last year, Cushman & Wakefield broke the site into four potential parcels.

But Goldwasser said then the massive property could still be sold in its entirety or in pieces.

Garza said Cushman & Wakefield did a good job of “re-marketing and re-branding” the U.S. Steel site to overcome the impression that, “If Dan McCaffery couldn’t do it, I don’t think I can do it, either.”

They also “thoroughly vetted” all 13 bidders before narrowing the list to three finalists scrutinized even more to make certain “they had the financing, know-how and experience to do something this big,” the alderman said.

Although 12,000 homes and a factory to build them is still incredibly ambitious, Garza said she is confident that Barcelona Housing can succeed where McCaffery failed. She noted that company officials “took their time to learn about the neighborhood and find out what people want here.”

In addition to building the plant and modular homes in four phases of 3,000 homes each, the new plan calls for retail and recreational space, she said.

“With their know-how, their capital and the people they have working with them, I have the utmost confidence they’re gonna do this. I’ve seen some of the work that they’ve done in Barcelona and it’s really incredible. They can build a three-flat in like 30 days. It’s all up to code. . . . We’re not gonna have to wait 20 years to see movement,” Garza said.

“They don’t have to dig a foundation. They screw pylons into the ground. They can withstand a 7.8 earthquake. . . . It’s just a new technology. The factory is going to be huge to build this much of a development. And once we start building homes, three-flats and four-flats, then come the stores and the other amenities. They incorporate a lot of green space and green technology. Access to the lakefront for all. Stuff that’s been really important to this neighborhood for a very long time.”

McCaffery wished Barcelona Housing the best. He not only hopes they can pull it off, he believes they can and probably will.

“They have ready money. As I understand it, they’re a very large company with very large backers. Cash is king,” McCaffery said.

“My plan was, I would have to say, a bit more ambitious and, perhaps time has shown it was too ambitious. Maybe I was being too Burnham-esque in making no small plans. . . . A company that can come up with a plan and the financing to execute that plan is wonderful. It’s terrific. I congratulate them.”

McCaffery said modular housing has made great advances and can work in Chicago to reduce the purchase price. He noted that he built the U.S. Embassy compound in Albania with modular housing. “It’s just beautiful.”