Rock Ventures LLC plans to include 33,000 square feet of ground-floor retail in a new parking garage it’s building in Detroit’s central business district. The 535,000-square-foot, “z-shaped” retail and parking development will help alleviate parking issues downtown while bringing more unique retail and dining options to the fast-growing, technology and creative corridor, Dan Gilbert, founder and chairman of Rock Ventures and Quicken Loans, said in a release. The district has added 10,000 new employees over the last two years, 6,500 from his companies alone, Gilbert said. The project will “zigzag” from the corner of Broadway and East Grand River to the corner of Library and Gratiot, Rock said. Rock Ventures plans to begin construction on the development this month and expects it to be completed by December 2013. Rock Ventures’ Bedrock Real Estate Services LLC will manage the development and lease the retail space. Southfield-based Neumann/Smith Architecture is architect on the project, and parking consultant Rich & Associates Inc. in Southfield is consulting on the structure’s design. Colasanti Construction Services Inc./Sachse Construction, a joint venture of Detroit-based Colasanti and Birmingham-based Sachse, are the construction managers for the project.