Hours before city officials showcased a street renovation proposal that includes closing off a main artery in Jackson Park to incorporate the land into the Obama Presidential Center, the Obama Foundation on Wednesday put some cash on the table: The Foundation will pay for a garage on adjacent city land.

The garage would be on a portion of the Midway Plaisance owned by the City of Chicago. Though the garage will be built above ground, it will be topped with a 3- to 4-acre landscaped area the foundation is calling a “park” — with a picnic and children’s play area and “more,” the foundation said.

The foundation’s willingness to pay for the garage — and the timing of the announcement, on the day the Chicago Department of Transportation unveiled its proposed road closures and expansions to accommodate the park, suggests that it is part of a deal — a peace offering — to sell to the people concerned about losing Cornell Avenue, as it passes through Jackson Park.

To make up for the Cornell closure between 59th Street and Hayes Drive, as well as closing Marquette Drive between Stony Island Avenue and Richards Drive, the city has proposed adding a new southbound lane to Lake Shore Drive between 57th and Hayes, CDOT Commissioner Rebekah Scheinfeld announced at a public open house on the proposal at the South Shore Cultural Center.

The city also says adding two lanes, one northbound and one southbound, to Stony Island between 59th and 63rd streets, will help keep travel times “about the same,” Scheinfeld said.

The garage would hold up to 450 cars. No cost estimate was provided. The site is on the Midway Plaisance bounded by Stony Island between 59th and 60th, near the 59th street Metra Station.

An issue still to be resolved: The Foundation pledged to replace Jackson Park land it is taking for the Obama Center with other parkland. It appears that the Foundation wants to set the stage for making the argument that the landscaped garage roof, with its amenities, will be seen an acceptable trade for the Jackson Park acres.

“Sounds like an interesting idea, but is it really a park?” asked Margaret Schmid, a coordinator of the Jackson Park Watch, which is keeping close tabs on the lakefront development.

Adding to the point about selling this as a park, the Foundation is branding this garage as a “combined park and parking facility.”

The overhaul is part of the city’s plan to make way for the Obama Center and the proposed merging of the golf courses in Jackson Park and at the South Shore Cultural Center.

The Chicago Sun-Times in a Tuesday story raised concerns about the lack of transparency from City Hall, the Chicago Park District, the Chicago Department of Transportation and the Obama Foundation about the lakefront redevelopment.

The foundation said in a statement: “Pending input from the community and approval by the City Council, the City would convey rights for parking to the Obama Foundation.”

The garage would be across the street from the Obama Center complex, which now includes a museum, women’s and community garden, a forum, office space, library, wooded walk, sledding hill and proposed athletic center. The library itself would be far smaller than the buildings for the forum — an event space — the museum and related offices.

Despite the expansions of Lake Shore Drive and Stony Island, Scheinfeld said changes around Jackson Park would see a net gain of at least 3 acres of parkland.

But street parking is significantly reduced in a series of other roadway tweaks, including the removal of parking on Hayes.

“We’re still looking at ways to make up for parking,” Scheinfeld said.

Officials have yet to say how much the road changes would cost, or where the money would come from.

Charlotte Mays, a Calumet Heights resident and a golf course regular, said she was wary of the city’s proposal Wednesday afternoon at the cultural center.

“Things work well for people around here as it is. It’s a lot of money and a lot of parkland that they want to take up,” Mays said.

Steven Evan said he came to the presentation expecting to find problems with the plan, but came away impressed.

“If they can keep it convenient for community residents, this could be a boost to the neighborhood like The 606 was for the Northwest Side,” he said.

A full description of the proposed road closures and expansions is posted at www.southlakefrontplan.com.

CDOT will hold another public open house with information and officials on hand to answer questions, from 4-8 p.m. at the South Shore Cultural Center, 7059 S. South Shore Drive.