Phases 3 and 4 will extend the line south from 63rd Street to Houston Street and Hanover Square, respectively. As part of Phase 3, a connection to the IND 63rd Street Line would be built, allowing for non-revenue moves into Queens. This connection will be constructed through underground drilling and blasting. Bellmouths already exist for this connection east of the Lexington Avenue–63rd Street station. This section, like the rest of the line, will mainly consist of a two-track line. However, between 21st Street and 9th Street, two additional tracks will be constructed on either side of the main alignment to allow for the storage of eight trains. This location was selected due to the sufficient depth of the area. The third phase would pass above several East River tunnels, including the 63rd Street Tunnel, the 60th Street Tunnel, the 53rd Street Tunnel, the Steinway Tunnel at 42nd Street, and the East River Tunnels at 32nd and 33rd Streets.