A longtime Portland developer and Old Port landowner is requesting a zoning measure that could pave the way for construction of the city’s tallest building.

Tim Soley of East Brown Cow Management Inc. is asking city planners to award height bonuses to developers in the Old Port area who create publicly accessible open space on their sites and protect that open space with public easements.

If his request is approved, Soley would be able – and appears ready – to submit plans for a building of more than 20 stories on what’s now a parking lot in the middle of the block bounded by Middle, Exchange, Fore and Union streets.

“Portland is experiencing unprecedented growth, and the number of undeveloped downtown lots will continue to shrink,” Soley said in a written statement. “We’re excited about our vision, as well as the potential for the creation of other invaluable public space downtown.”

Soley said zoning language for the B-3 business zone encourages developers to build from lot line to lot line for maximum profits and discourages the preservation of open space downtown. He says awarding height bonuses would serve the dual goal of preserving open space and protecting the financial viability of a new development project.

It’s unclear how the zoning amendment will be received by city officials, elected representatives and the general public.

The proposal was just submitted to the city and has not yet been reviewed by staff. Portland is in the middle of rewriting its entire land use code.

Such proposals are first reviewed by the planning board, which will make a non-binding recommendation to the City Council.

Historically, some Portland residents have shown an aversion to tall buildings.

A group of residents successfully sued the city in 2014 after it approved a series of 14-story buildings in Bayside, forcing the developer to scale down the project, known as Midtown. That project is now the subject of litigation between the city and Florida-based Federated Cos.

And Munjoy Hill residents tried unsuccessfully to enact an ordinance by referendum in 2015 to protect scenic view corridors. That effort was in response to plans to redevelop the former Portland Co. complex at 58 Fore St. The master plan for that project, Portland Foreside, includes a nine- to 10-story office building.

The zoning text amendment proposed by Soley would more than double the allowable height for some downtown parcels, including the Canal Plaza block at Union and Middle Streets, which Soley owns.

Soley has expressed interest in creating a 23-story building on the surface parking lot behind the Fore Street Parking garage in the past.

Tim Soley’s zoning application includes an artist’s rendering of a slender building rising high above the buildings along Exchange Street. Courtesy of Woodard & Curran

When discussing his concept in 2016, he said the market at that time would not support office uses, suggesting it would either have to be hotel rooms, apartments or condominiums. It’s unclear whether the market for offices has changed.

In June, a rendering of Portland’s downtown skyline with a tall building in that vicinity began circulating on social media and in development circles.

The zoning application filed with the city on Dec. 11 shows an artist rendering of a slender building – with two-story windows and a terra-cotta facade – rising high above the typical three- or four-story buildings along Exchange Street.

The application references “an airy lounge and restaurant with vaulted wood ceilings” and floor-to-ceiling windows affording a 360-degree view.

It also shows a series of eight sidewalks/pedestrian pathways leading to the new building and open space that would include stone benches, tree planters and a new cafe with glass walls that could be opened during warmer weather.

Soley said in his statement that, if the text amendment is approved, East Brown Cow would submit a site plan for a new building.

“At that point, we will have developed final project designs and will be very excited to discuss them and answer any questions,” he said.

A portion of his application showing how the height bonus would be awarded shows how a 10-story, 125-foot-tall  building could be turned into a 23-story, 287-foot-tall building.

Current zoning rules limit building heights at Canal Plaza to 125 feet, according to the city’s Downtown Overlay Map. The tallest buildings allowed on the peninsula are in the area bounded by Cumberland Avenue and High, Congress and Elm streets, where height is capped 210 feet.

Soley said the proposed zone text amendment would allow for a building height of up to 299 feet, or a roughly 25-story building. The text amendment is not specific to Soley’s property and would apply across the B-3 zone.

If approved, Soley would be allowed to build the city’s tallest building to date.

Franklin Towers, a low-income housing complex operated by the Portland Housing Authority, is currently the city’s tallest building at about 175 feet and 16 stories, while the 13-story West Portland Harborview stands at 168 feet, according to the real estate data website Emporis.

Other downtown buildings of notable height include the 15-story Back Bay Tower, 14-story Time & Temperature building and the 10-story Maine Bank & Trust Building. And the spire of the Cathedral of Immaculate Conception is about 200 feet tall.

Soley has recently invested millions of dollars into Canal Plaza and other facilities he owns on the block bounded by Middle, Exchange, Fore and Union Streets. He’s added a solar array to the Fore Street parking garage and renovated the Canal Plaza, adding a tear-drop shaped building that is now home to the Copper Branch restaurant.

He’s also built the new Hyatt Hotel at the corner of Fore and Union streets.

Soley said a taller building, taking up less of a footprint in the surface parking lot located in the middle of the block, would help revitalize the block and secure more open space in the Old Port.

“The site is better served by a taller, slender building and a new plaza, which we envision as an inviting oasis within the Old Port featuring new seating, planting, artwork and lighting,” he said.