The track connections from the new station to the 63rd Street Tunnel were excavated using tunnel boring machines. The first machine was delivered in May 2007. Dragados/Judlau created a launch chamber for the tunnel boring machines under Second Avenue at 63rd Street in Manhattan using a controlled drill-and-blast method, then assembled and launched each 640-ton machine. The first tunnel boring machine was launched westbound then southbound from the 63rd Street Tunnel in September 2007, and it reached Grand Central Terminal in July 2008. The second machine began boring a parallel tunnel in December 2007 and had completed its tunnel at 37th Street on September 30, 2008. Geocomp Corporation was hired to monitor the boring, using a battery of instruments to record vibration, ground settlement and any tilting or drift suffered by the tunnel boring machines. The instruments include inclinometers, extensometers, seismographs, observation wells, dynamic strain gauges, tilt meters and automated motorized total stations with prismatic targets. The tunnel boring machines bored an average of per day. Cross-connections between the tunnels were created under Park Avenue, between 49th and 51st Streets, by controlled drill-and-blast. The work began in mid-July 2008 and required between six and eight months to complete.