The MTA has begun an environmental review for a proposed westward extension of the Second Avenue Subway beneath 125th Street in Harlem. The agency released a draft scoping document setting out studies of the project's potential effects on Central Harlem.

The plan would extend the Q line west to Broadway. The MTA is exploring whether it could use the large tunnel-boring machines now working on Phase 2 beneath East Harlem to continue digging under 125th Street.

Residents can comment on the scoping document through Nov. 13, either by mail or at public meetings. Two virtual sessions are scheduled for Oct. 22, from noon to 2 p.m. and 6 to 8 p.m. An in-person meeting is set for Oct. 27, from 6 to 8 p.m., at the Adam Clayton Powell, Jr. State Office Building.