In 1989, the Massachusetts Water Resources Authority (MWRA) issued a planning and design contract for a second transmission main to provide redundancy for the Hultman Aqueduct.

[2] During feasibility studies, it was recognized that costs and environmental and community impact issues related to reconstruction of the Sudbury Aqueduct through an urban/suburban area compared unfavorably with a full length tunnel in rock, deep under existing structures and facilities.

The alignment of the tunnel generally coincides with the existing Hultman Aqueduct and is constructed in permanent underground easements below several hundred private properties.

Connections to serve community clients resulted in the five small diameter riser shafts to supply water to customers along the tunnel alignment.

The design transient pressure was determined by hydraulic analysis of the overall future transmission system, including accounting for characteristics of control mechanisms, e.g., shutting times for major valves or catastrophic type changes in flow rate.

Incorporated into the design are considerations for filling and unwatering (e.g., air release/vacuum valves, filling/unwatering procedures and requirements for pumping), as well as the need and means for metering of flows during operation.