One of the 2022 Trenchless Technology Rehabilitation Project of the Year Honorable Mentions is the M29 Outfall Improvements project. Projects of the Year are awarded in two categories – New Installation and Rehabilitation – based on the following criteria: technical advancements, technical complexity, milestones and records, interaction and cooperation, and industry advancement.

JMT designed trenchless rehabilitation improvements to enhance the water quality and increase the structural integrity of the M29 combined sewer outfall (CSO) culvert on the Monongahela River in Pittsburgh, PA. The 15-foot diameter, 450-foot-long CSO was initially built in the 1800s to culvert a stream and provide land for a steel plant operation along the Monongahela River. Today, the M29 outfall serves as the second largest CSO in the City of Pittsburgh and is a significant portion of the combined sewer interceptor network. The M29 outfall was inspected and found to be in severe disrepair, requiring structural lining to prevent the system from collapsing and causing a catastrophic failure.

As a consultant to Pittsburgh Water and Sewer Authority, JMT evaluated several replacement, repair, and trenchless rehabilitation options, given the culvert’s size and limited accessibility. A physical scale model of the culvert and outfall was built to simulate the interaction between the combined sewer system and the Monongahela River.

The final construction included filling significant voids in the brick walls from inside the structure, lining the brick culvert walls with shotcrete, reforming and establishing a new concrete invert, applying an epoxy corrosion inhibitor on all surfaces, and replacement of the existing stone endwall with a new cast-in-place concrete endwall. The endwall also included a 15-foot metal flap gate to control river intrusion into the combined sewer system, relieving a major hydraulic bottleneck upstream.

Congratulations to our team members and all other award winners!

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