This aqueduct starts at the John J. Carroll Water Treatment Plant in Marlborough, Massachusetts, and ends at an MWRA terminal in Weston, Massachusetts. It is about long (28.3 km) and is constructed far below ground level, mostly in bedrock. It includes several vertical risers called shafts, lined with steel, used to make connections throughout the system. It is built underneath portions of Marlborough, Southborough, Framingham, Wayland, and Weston, Massachusetts, with a wye intersection 235 feet (71.6 m) below the Massachusetts Turnpike former toll booths at State Route 128.