In a grassy field flanked by abandoned and graffiti marked mansions in historic Brush Park, blocks north of Comerica Park, Detroit Mayor Mike Duggan and a host of investors on Wednesday announced a massive $70-million housing development lead by billionaire Dan Gilbert's Bedrock Development.

The project calls for new construction on 8.4 acres of land of 337 housing units, commercial development and the renovation of four historic Brush Park mansions, including the Ransom Gillis home at 205 Alfred Street, which was built in the the 1870s for the wholesale and dry good merchant. The press conference was held next to three of those mansions marked for renovation. The fourth one was just down the street.

"We have four historic homes dating back to the 1800s and the first criteria we put out is that any developer has to restore those homes," Duggan told the crowd. " We are going to preserve our history, and build around them, not just bulldoze it and start again. And so I'm really pleased that we are keeping the best of the past."

Mayor Duggan at the press conference. He said nine bidders submitted proposals.

Bedrock will be the majority investor. It marks a new start for the company in its move into the neighborhoods after pouring millions of dollars into commercial and residential buildings in downtown and Corktown. Matt Cullen, chief executive officer of Rock Ventures, a Gilbert company, said that the organization has interest in continuing to develop in neighborhoods.

The minority investors in the project, Brush Park Development Investors, include Marvin Beatty, Darrell Burks, Freman Hendrix, Pamela Rodgers and Sam Thomas.

The development will focus on a four-block area bounded by Edmund Street to the north, John R to the west, and Alfred to the south.

One of the historic mansions slated for renovation.

At least 20 percent of the housing will be affordable housing.

The housing stock is expected to include for-sale and for-rent housing. The development is expected to offer apartments, townhomes and flats.

"We're building a neighborhood that's going to be available to everybody," Duggan said.

Marvin Beatty, one of the investors, speaks at the press conference.

People chatting before the press conference.