PORTLAND, Maine — The Planning Board took its first look Tuesday at a proposed housing and retail complex that would transform the Portland skyline.

It also discussed plans to renovate a downtown building for use as a charter school.

Tuesday’s workshop did not require the board to take any action on the proposed Maritime Landing complex, which calls for building seven towers, up to 12 stories tall, on 3.24 acres of city-owned property along Somerset Street in the Bayside neighborhood.

But members expressed support for it — and also sounded notes of caution.

The complex would include more than 90,000 square feet of retail space, 1,100 parking spaces and 675 market-rate apartments.

In September, the City Council approved terms of an agreement selling the property, formerly the site of a rail and scrap yard, to developer Federated Cos. for $2.2 million.

The deal also gives Federated a $9 million grant to help build a 700-space parking garage in the project’s first phase. That part of the project, estimated to cost $38 million, would include building two of the towers with a total of about 200 one- and two-bedroom apartments. The towers and the garage, all on the east side of Chestnut Street, would be constructed within the next three years.

On Tuesday, the board discussed zoning changes that would be necessary for the project to continue moving forward. The changes would allow Federated to build a 158-foot tower in a zone that is currently limited to structures no taller than 105 feet.

The changes also would give the developer some leeway in meeting a requirement that floors above 125 feet from street level be set back from the building’s perimeter. Instead of being mandated by the zoning rules, any setbacks would be considered when the board reviews the site plan for the project.

In addition, the board discussed proposed changes in the site plan review process that would allow Federated to submit a master plan for the entire project, and extend the life of its potential approval from three years to six years.

“[Maritime Landing] could set a standard for the neighborhood that would add to its allure and bring in retail business,” board member Timothy Dean said.

Board member Bill Hall said, “If the project goes forward, it could be transformative for Portland.”

But Hall said he also was concerned about the “monolithic” appearance of the towers. If built as planned, four of the towers would soar above the nearby 10-story Intermed building at 84 Marginal Way.

That was a concern shared by Portland resident Don Elliot, who said he worried that such tall buildings would create “canyons” in the area and obstruct views of the city skyline.

“The setback [requirement] is there for a reason,” he said. “I urge people to keep in mind the scale of the buildings and the scale of the city.”

Tuesday’s discussion was only the first step in the process. The board must still hold another workshop and a public hearing on the zoning and site plan rule changes, and then forward its recommendations to the City Council for approval. The project must then undergo a formal site plan review.

The approval process is expected to continue through late March 2013.

In other business, the board discussed plans for renovating a building that will house the recently approved Baxter Academy for Technology and Science.

On Nov. 16, Baxter received approval from the Maine Charter School Commission to open next September. Baxter, which will be in an existing building at 54 York St. at the corner with Maple Street, will be Maine’s third — and Portland’s first — charter school.

But before classes start, the school must receive approval to overhaul the three-story building, which is owned by Rufus Deering Lumber Co. The $185,000 project will include the construction of a handicapped-accessible entrance ramp, but no other exterior changes.

The Tuesday workshop focused on managing traffic around the school as its projected 320 students come and go. Plans calls for students arriving by car to be dropped off at the intersection across York Street from the school, while chartered buses would deliver students to an entrance on Maple Street.

But board members wondered if the drop-off spots should be switched, with cars going to Maple Street and buses using the York Street unloading area. And board member David Silk suggested that staffing the York Street intersection with crossing guards should be a condition of the project’s approval.

Other suggestions included moving the site of a proposed crosswalk so that students could cross York Street closer to the school entrance.

The school must respond to comments from the board and city planners and then submit a formal application for site plan review.