Marlborough, MA

Massachusetts Water Resource Authority, Walnut Hill Treatment Plant, Cosgrove Intake Pipeline

Scope/Solutions
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Project Summary

Scope/Solutions

The Cosgrove Intake pipeline, a 144 in. dia. prestressed concrete cylinder pipe (PCCP), at MWRA’s Walnut Hill Water Treatment Plant Project was completed in early 2004 as a part of the water supply system for the City of Boston. Less than a year after construction of the pipeline, a large leak of approximately 700 gpm developed near a deep manhole chamber in a section of the pipeline with multiple elbows. SGH provided emergency response and evaluated the risk of failure resulting from the leak, inspected the pipeline to determine the cause of the leak, and developed a repair scheme.

For this project, SGH:

Performed internal inspection of the leaking pipe using a diver during a brief shutdown while the line was in operation
Evaluated the structural safety due to the combined effects of internal pressure, dead loads, prestress, and hydraulic pressure-induced thrust at elbows
Internally inspected and measured all harnessed joints to determine if any joints opened more than the design limits, inspected the pipeline for visible signs of anomalies, and externally inspected the leaking joint
Designed repairs that included welding of the leaking joint and soil grouting.