A plan to redevelop the old Bayside Expo site on Columbia Point envisions a mix of office space, labs, retail, along with as many as 1,450 units of housing over 3.5 million square feet, according to a document filed today by Accordia Partners LLC, the team that signed a 99-year lease with UMass Boston last year and that will manage the build-out of the 20-acre waterfront site, along with another large parcel occupied by Santander Bank at 2 Morrissey Blvd.

A three-page “Letter of Intent” that Accordia filed with their initial plans to the Boston Planning and Development Agency is the first step in a city-led public process that will likely take a year or more to complete.

The two men who co-own Accordia— Dick Galvin and Kirk Sykes— have said they hope to build the project with the expectation that it would be in part a technology hub that would, among other things, present opportunities for jobs for UMass Boston students.

The letter of intent also includes a brief discussion of 2 Morrissey Blvd., which Accordia also controls. That site is now occupied by Santander Bank, which remains a long-term tenant on the property. Accordia paid $110,000,000 for the 2 Morrissey parcels, which include five buildings and a total of 425,000 rentable square feet.

The letter gives a general overview of the project’s likely scope, size, the mix of uses, and an estimate of the number of housing units. Much of the outline will be familiar to residents who have participated in public meetings organized by civic groups and Accordia last year, including two “Citizens Connect to Bayside” planning meetings held last fall, which the Accordia team has credited with helping them develop their vision.

The letter reads in part: “The new project is proposed to include approximately 3.5 million square feet of development on the UMBA property and approximately 2.4 million square feet of development on the 2 Morrissey Boulevard property, for a total of approximately 5.9 million square feet of development. The development is proposed to include 1,460,000± square feet of residential development (to comprise approximately 1,740 new units of housing), 4,006,000± square feet of office, research and development, life sciences and/or academic uses, as well as 155,000± square feet of ground floor retail/restaurant/cultural/civic space."

The next step in the process will be the filing of a Project Notification Form (PNF), at document that will provide much more detail about the plan, according to Richard Galvin, who spoke to the Reporter last week.

Galvin said the PNF will include specifics on the breakdown of housing units, infrastructure planning and an attempt to make Accordia’s “T to the Sea” vision a reality.

“The whole theme of open space is providing connections to the water,” said Galvin. “We really hope that the ‘T to the Sea,’ starts at Mt. Vernon [Street] and is a straight visual shot right to the water.”

None of the residential units envisioned in Accordia’s plans at the moment are intended for undergraduate students, Galvin said.

“There might be some appeal to graduate students with our compact living units, but we won’t have dorms,” Galvin said. “Our strategy with housing is to hit a lot of different price points — with market-rate, mid-range, and affordable prices— and that largely gets driven by unit size, so we do expect to have some compact units.”

Under the Bayside lease agreement with the UMass Building Authority, Accordia Partners is expected to pay UMass anywhere from $192.5 million to $235 million in a lump sum. The exact amount will depend on the amount of the square footage that is permitted for construction.