Developers with sights set on Red Hook and Sunset Park have laid out imaginative plans that include about 40 million square feet of development and a brand new subway line to Manhattan.

Global engineering firm AECOM released renderings in three scenarios of what they might do with the waterfront real estate in southwest Brooklyn. Two of the possibilities will include 45,000 new residences and a new 9 train that would extend from Manhattan’s 1 line and connect to Park Slope.

Those two scenarios require building from scratch new subway infrastructure, including three new substations, that would, according to the plan, be funded by revenue from the new residential development.

Chris Ward, the chief executive of AECOM, stated that as a socioeconomic region Red Hook and the largely industrial Sunset Park are particularly accommodating to more population density that would not displace the existing community. But the group’s report states that a population influx of the proposed size cannot be accommodated without substantial infrastructure and open space improvements.

The three new subway stations would be at Atlantic Basin near where most of the development is planned, on Lorraine Street, and at Fourth Avenue and 10th Street in Park Slope with connection to the F, G and R trains.

Those scenarios which require new subway infrastructure, propose to add 35 million to 45 million square feet of redevelopment, including the affordable housing now mandated by the city on new development. There will also be large public spaces and parks, and consideration of coastal protection in flood-prone zones.

AECOM estimates $90 million to $130 million in annual revenue from bigger proposals.

AECOM’s third and smallest redevelopment proposal would add 25 million square feet of usable space and would not require new subways, and do not include parks and pedestrian improvements.

The group is emphasizing that the proposals are still very preliminary.

“This is meant to be a starting point for a conversation,” Ward said.