The conversion of the Government Center garage into a large mixed-use complex will require the temporary relocation of the Haymarket bus terminal and might require the shutdown of the Green and Orange Line stations underneath that, state transportation planners say. But HYM, the company that has started tearing down the garage for a six-building complex with 800 residential units, a 200-room hotel, 1 million square feet of office space and 82,000 square feet of retail space, says it is not expecting any complete shutdown of the subway station:

In December of 2020 we plan to begin deconstructing the section of the garage above the Haymarket bus terminal and T station, and the section that spans Congress Street. In preparation for this work, the MBTA is assessing any potential impacts on service at the Haymarket bus terminal and T station. In the next 10 months, we will be working with the MBTA, the City of Boston and the community on a plan for temporary bus stops until work on the new Haymarket terminal is completed. We will also work with the MBTA to ensure there is sufficient notice, signage and time for the public to prepare for any temporary impacts on bus or train service, and to minimize any disruptions in service. We are not planning to shut down the Haymarket MBTA station, but construction elements may affect specific head house entrances or exits.

HYM's statement comes after the state's Central Transportation Planning Staff released a memo on an effort to plan the Haymarket station's future, both during construction and for the next 40 years:

A temporary closure of the MBTA Haymarket Station and the subsequent rerouting of bus routes is a possibility given the structural engineering requirements and conditions of the Bulfinch Crossing project. This is due to the temporary relocation of the Haymarket bus terminal along with the temporary closure of Congress Street, due to the demolition of the garage above it. Haymarket Station currently serves a significant number of transit routes, including the Orange Line, the Green Line’s C and E lines, and eight MBTA bus routes. This work scope will support the MBTA in the ongoing review and coordination of the developer’s plan to transform Bulfinch Crossing into a dense mixed-use development that will impact MBTA service in the short- and long-term.

At the request of the MBTA, the planners will also look at possible transportation requirements in a half-mile radius around the station for the next 20 and 40 years - although in their memo, the planners acknowledge they have no data to plan that far out, but will try to extrapolate from the data they do have.

H/t Ted.