Redevelopment of the 161-acre Suffolk Downs property could include approximately 11 million square feet of residential and commercial development in East Boston, including a fast-tracked 500,000-square-foot office building if Amazon selects the site for its second headquarters.

Boston-based HYM Investment Group on Wednesday submitted formal notification of its plans for the 109-acre Boston section of the property in a two-page letter of intent to the Boston Planning and Development Agency. Detailed designs will follow in early December, HYM Managing Director Thomas O’Brien said today.

HYM has hired Boston-based CBT Architects to design a 500,000-square-foot office building with the goal of meeting Amazon’s completion date of 2019 for the first phase of its “HQ2” project, he said.

“We’re spending money and putting ourselves in a position that we’ll be included in the next round,” O’Brien said. “In order to keep moving on that process, our firm strategy is to continue to be ready to deliver that building in 2019. To do that, we have to move now from a permitting and design perspective.”

The overall project would include housing, retail, office, labs and hotels, with 40 acres including wetlands set aside for publicly-accessible open space and recreation areas. Buildout would take place over 15 to 20 years.

Boston Mayor Marty Walsh and Revere Mayor Brian Arrigo jointly submitted a proposal to Amazon last month showcasing Suffolk Downs as the prime local site for the e-commerce leader’s 8-million-square-foot second headquarters. Amazon said it wants to occupy a 500,000-square-foot office building in 2019 in the first phase of the project. To meet that timetable, HYM said it may submit an expedited large project review to the BPDA for a single 500,000-square-foot building.

Retail space would be anchored in a pair of districts called Beachmont Square and Belle Isle Square, along with a Main Street-style shopping district. Housing would include a mix of townhouses, apartments, condominiums and senior housing.

Plans for the 52-acre Revere portion of the site will be filed as soon as late November, O’Brien said. He declined to give specific density but said the majority would be commercial space along with housing.

The proposed density in Boston, with a floor area ratio of 2.3, requires zoning relief in the form of a planned development area, a zoning overlay which can be applied to large or complex projects.

In Revere, the project needs approval of at least eight of the 11 city councilors for a special permit.

Boston and Revere’s Amazon bid contained additional details about potential development at the site if it wins the nationwide competition which attracted bids from 238 cities and regions. The document lays out plans for 10,000 housing units, 550,000 square feet of street-front retail and five hotels with more than 1,500 rooms.

HYM acquired the long-sought-after property for $155 million in May. The racetrack, which opened in 1935, held its last regular scheduled races in 2014 but has operated a limited schedule of live racing on eight weekends this year.