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Massachusetts Water Resources Authority


Updated December 28, 2022


MWRA Public Affairs

Weston Aqueduct Supply Main PRV Improvements (Contract 7563)

About this Project:

This Project was developed as an interim improvement to enhance MWRA’s emergency response to a failure of the Metropolitan Tunnel system until a redundant tunnel is constructed.  The Project is to replace pressure reducing valves on the Weston Aqueduct Supply Main (WASM) 4 at Nonantum Road in Boston and WASM 3 at Mystic Valley Parkway in Medford to increase the supply from the Northern Low Service System and reduce the need to pump non-potable water out of the Spot Pond Reservoir in an emergency.  The new larger pressure reducing valves at Nonantum Road and Mystic Valley Parkway will be designed to be controlled remotely through SCADA.  The Northern Low Service pipeline would operate at increased grade lines to supply additional flow to the Spot Pond Pumping Station and Storage Facility and the Gillis Pumping Station in an emergency condition with the tunnel system out of service.

The contract will demolish the existing Nonantum Road and Mystic Valley Parkway PRV vault structures, including four 24-inch PRVs and appurtenances, and construct new larger cast-in-place vaults.  At Mystic Valley Parkway, two 42-inch PRVs and at Nonantum Road two 30-inch PRVs, isolation valves, piping, and other appurtenances will be installed.  Additionally, a new master meter will be constructed at the Mystic Valley Parkway pressure reducing valves and the existing master meter located near the Nonantum Road Pressure reducing valves will be upgraded to accommodate the increased flow.

Work will be sequential, starting at the Mystic Valley Parkway PRV Vault, followed by the Nonantum Road PRV vault.  The construction duration is 24 months.

Project Updates

December 28, 2022

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Recently Completed:

  • Completed W14 pipe and PRV installation
  • Completed ductbanks at W14
  • Started Demo at W16


  • Complete butterfly valve installation at W14
  • Continue with new vault at W16

W16 Construction forms for base slab

Steel pipe and PRVs delivered

W16 Placing rebar for the North and South walls of the PRV Vault

W14 ductwork for power and cabinet pedestal set up

Butterfly valve installation at W14

November 3, 2022

W14 PRVs Installed

W14 Outside Piping

Applying tape at welded joints at W14

W16 Demo of existing PRV vault

Screening was pulled back to improve sightlines for vehicles exiting parking lot.

November 3, 2022

Construction updates will be posted here.

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Updated: December 28, 2022
Original Post: November 3, 2022