The Ohio State University Wexner Medical Center is one step closer to making history in Powell.

The city's planning and zoning commission Aug. 8 voted 5-1 to approve the preliminary development plan for an ambulatory-care center on about 30 acres at 3315 Royal Belfast Road, at the northeast corner of Home Road and Sawmill Parkway, across from Liberty High School.

The site is in the process of being annexed into the city from Liberty Township.

The project includes two phases, the first of which will be the construction of a 150,000-square-foot, 5-story ambulatory-care center and a 2-story building with another 56,000 square feet of space.

Plans call for a 1,500-space parking lot and access off Sawmill Parkway.

In addition to the ambulatory-care center, the first phase would house specialty care, diagnostic services such as MRIs and X-rays, and offices for primary-care physicians, internists and mental-health professionals.

A second phase would add 216,000 square feet of space and could include a "micro-hospital."

The university hopes to have the final development plan and annexation approved by November, said Aaron Underhill, an attorney representing Ohio State. No timetable for construction has been announced.

Ohio State anticipates the site will employ 500 people and have an annual payroll of $50 million.

If approved, this would be the largest project in the city's history and its largest employer. The 5-story care center also would be the tallest building in Powell.

Commission member Shawn Boysko voted against the plan because officials provided few details on what the buildings will look like.

"There's really nothing about the building. I'm not sure how we review a preliminary plan without any building information," Boysko said. "I feel like I don't have enough information. I respect and appreciate what OSU has done in the past and what they will do here, but without seeing it, it leaves a lot to the imagination."

The university is working on a similar project at Hamilton Road and state Route 161 in Columbus.

Officials said its design would be used as the basis for the Powell location and the university expects to have more detailed architectural plans in four to six weeks.

"It's evolving. We have a very complicated architectural design process at the university; there's a lot of points of input," said Keith Myers, vice president of planning and real estate for Ohio State. "We're not going to bring the exact building here, but it's the model that we need to get through. The building will be a fairly contemporary building. It's important for us to have a lot of glass in the building -- daylight is important in health care and we're going to be working to try and maximize that as much as we can."

Ohio State provided more details on other aspects of the project.

The university expects to draw patients from a 5- to 10-mile radius, said Dan Like, executive director of ambulatory services with Ohio State.

"We're really excited about our growth into the different communities in Columbus," Like said. "We recognize the need to get out into communities where our prospective patients live and work, to allow people to have services and not have to come to campus."

The hours of operation are expected to range from about 5:30 a.m. for surgical cases to as late as 9 or 10 p.m. for urgent care, Like said. Most other hours will be 8 a.m. to 5 p.m., he said.

Despite rumors, there are no plans for a helipad at the site, officials said.

Commission members urged Ohio State to continue meeting with neighbors and work to minimize concerns over light pollution, traffic and signs.

Officials from the city and county also are reviewing a traffic study to determine what road and traffic-control improvements may be required for the development.

The next planning and zoning commission meeting is scheduled for 7 p.m. Aug. 22 at the Village Green Municipal Building, 47 Hall St.