Developers who own the Portland Co. complex are asking the city to rezone the property, triggering concerns from neighbors on Munjoy Hill that new, taller buildings could block sweeping views of Portland Harbor.

The zoning request, submitted to the Portland Planning Board this month, asks for the 10-acre, waterfront site to be classified as mixed-use, potentially allowing CPB2 LLC, the new owner, to construct buildings as tall as about 65 feet in places.

“The goal is to try to maintain reasonable amounts of views from Munjoy Hill while allowing some infill development on this site,” said Jeff Levine, director of planning and urban development for Portland.

The zoning change is the first step toward redeveloping the historic complex, which its new owners have envisioned as a mixture of residential, commercial and office space. Close to the Old Port and downtown Portland, the development represents a considerable opportunity for the company and a potentially dramatic change for the city’s waterfront.

How tall the new buildings are in relation to Fore Street could vary widely depending on where the city decides to start its measurements.

When using the floodplain as a starting point, buildings would rise between one and two stories above Fore Street, according to documents submitted by the developer.

Using a starting point called the average grade – determined by averaging the altitude of a property’s corners – the potential for intrusions into the view of Munjoy Hill residents sprouts to between two and four stories above Fore Street.

The developers have yet to release more specific site plans, which usually include renderings or drawings of what the actual development would look like.

Levine said it’s too early for that level of detail, especially for projects where an approved zoning change could mean the difference between building the development or not.

But already, the rezoning application and potential building elevation levels are giving residents concern.

“That scares me to death,” wrote Denise Pressier in a letter to the planning board. “I can (envision) another mass half the height of the Portland House blocking the sun’s warmth and bird’s-eye views (that are) so breathtakingly wonderful now. I would encourage the City Council to not only walk the actual site but also take a stroll up the hill on Fore Street to experience this feeling of being on top of the world, a stop to catch one’s breath, and savor the breathtaking beauty of the working/recreational waters of Casco Bay.”

Another comment came from longtime Munjoy Hill residents Peter and Pam Macomber. In a similar plea to the Planning Board and City Council, the Macombers said they, too, revel in the view from Fore Street, where cruise ship traffic and the never-ending boats passing through the harbor make for a “magical” atmosphere. They also scoffed at the notion of “view corridors” contemplated by the city in a 2004 study, in which planners analyzed what of the surrounding vista would still be visible between future buildings.

“(View corridors) are tantamount to telling people to look through the wrong end of a telescope with blinders on,” the Macombers wrote. “Those corridors only compartmentalize and minimize the view and conceal more than they reveal.”

Before any zoning change is granted, the Planning Board will hold at least one public hearing, and a final decision would have to be made by the City Council.

Other processes remain, however. After the zoning question is decided, the Portland Historic Preservation Board is likely to consider designating either some buildings or all of the Portland Co. site historic landmarks. If the board decides that the entire 10-acre parcel is a historic district, development plans could grind to a halt.

“We’re hoping the developer has a good conversation with many of the abutters and takes into account as many of their concerns as they can,” Levine said.