Developers have submitted their first detailed plan to begin transforming 10 acres of former industrial land along Portland’s eastern waterfront.

Portland Foreside Development Co. filed a site plan application for the first phase of development of the former Portland Co. complex. That phase will touch three out of the six development blocks at 58 Fore St., plus the construction of a public plaza that will connect Fore Street to the waterfront.

Rendering of new offices for Sun Life U.S. to be built on the former Portland Co. complex on Portland’s waterfront

The initial phase will include a new office building on the westernmost portion of the site that is expected to be used by Sun Life U.S. and its subsidiary FullscopeRMS. Sun Life would join the payment processing firm Wex, which relocated to that area earlier this year. It will also include a local market hall, event space, housing, structured parking and other restaurant, retail and service uses.

“As a whole, this proposed development presents an unparalleled opportunity to grow the city’s tax base, add housing, and create jobs,” the application states.

A neighborhood meeting has been scheduled on Monday from 5-6 p.m. at the St. Lawrence Arts Center on Congress Street. And the Planning Board will conduct its first workshop on Tuesday.

The development of the former Portland Co. complex has been in the works for years.

Founded in 1846, the Portland Co. complex was built to connect Portland to Montreal by rail and was the first locomotive factory in the United States that brought all of the necessary shops and a foundry together on one site. It remained in operation for 137 years and was deemed eligible for the National Register of Historic Places in 1976.

Portland Foreside Development Co.’s site plans include a market hall that will showcase chefs and culinary-focused entrepreneurs. Rendering by Bruner/Cott Architects

The redevelopment efforts began with a controversial rezoning process in 2015 that prompted area residents to launch a citywide referendum to protect waterfront views that was ultimately rejected by voters.

A master development plan was approved in late 2016, locking in key programming and land uses.

At full build-out, the plan calls for 638 units of rental and resident-owned housing, 132 hotel rooms, nearly 60,000 square feet of retail space, a new marina and nearly 124,000 square feet of office space. A total of 736 parking spaces are proposed for the site, mostly on the ground floors of the buildings.

At least 10 percent of the housing units would have to be made affordable to middle-income residents. However, the developer could buy its way out of that requirement for $105,000 per unit. More than $6 million could be infused into the city’s housing trust fund, which provides incentives for affordable housing developments.

Development activity has been evident this year.

Over the summer, crews demolished buildings that were deemed to be noncontributing structures within the newly created Portland Company Historic District. Crews dismantled the historic Pattern Storehouse brick by brick so it could be rebuilt during this phase closer to the waterfront, where it’s expected to become a restaurant.

A new marina was also completed over the summer.

The city’s Development Review Services manager, James Rather, said last week that the staff was still working its way through the weighty application ahead of the Planning Board’s first workshop on Tuesday. Rather said the staff in the city’s bustling planning office was like “a snake trying to digest a wolf.”

“It’s a big project,” Rather said. “We’re still learning about the project. It’s still early, and there will be multiple workshops on this.”

Casey Prentice, a principal for the Portland Foreside Development Co., did not respond to requests for an interview on Wednesday or Thursday.

According to the project description, phase one will touch three of the six development blocks.

The westernmost parcel, Block 1, is located at the end of the newly constructed portion of Thames Street.

A new, 95,100-square-foot office space for Sun Life with ground floor retail is proposed for the upland side. And a reconstructed Pattern Storehouse, or Building 12, is proposed along the waterfront and is expected to be occupied by Evo restaurant with office space and two residential units above it.

Block 2 is located in the center of the site and referred to as the “historic core.”

Plans call for the restoration of seven historically significant buildings. One of the buildings is described as “Market Hall,” which will showcase local food and beverage vendors, chefs and culinary-focused entrepreneurs and retail space. The upper floors will consist of 17,900 square feet of event space and 12,400 square feet of office space. A total of 35,900 square feet of space will be devoted to retail, restaurant and other service uses on this block.

Blocks 1 and 2 will be separated by a public plaza that will be constructed within a 50-foot-wide public easement. The project summary states the plaza will include an “expansive public upper viewing level and a public lower plaza to provide for the enjoyment of views of both the rehabilitated buildings of the Portland Company Historic District and Casco Bay.”

Block 4 is located to the east of the historic core and comprises the last upland redevelopment site.

There, developers are proposing to build a five-level parking garage for 652 vehicles. The garage will be used as a foundation for a future residential building that will be built on top during a future phase. But the first phase includes 12 units of housing, totaling 12,900 square feet, along the west side of the garage. It’s unclear what type of housing that will be. And the south side of the garage will include 1,100 square feet of retail, restaurant and services uses.

The application also includes plans to relocate a portion of the Narrow Gauge Rail Road’s rail line farther inland, so an existing pathway can be relocated closer to the waterfront.

“From a planning perspective, it’s a transformative project for that area of the city so it’s pretty exciting to see,” Rather said.