Back Cove West Storage Conduit - Portland, ME

From the outset, the Sargent management team recognized the complexity of Back Cove West Storage Conduit project, including significant geotechnical risks, challenges with installing precast concrete storage conduit boxes below sea level, extensive ledge removal, and a constrained work area. Superintendent Adam Tenan played a pivotal role in devising strategies to address these obstacles, spending months reviewing plans and evaluating means and methods, ultimately landing on a value engineering proposal that was accepted by the owner.
One key innovation was the development of a double-wide 8-foot by 20-foot box culvert design, supported by 3D printed mockups and draft plans. This design allowed for the incorporation of 1,600 linear feet of 60-inch pipe storage at a higher elevation, reducing the width and depth of the precast storage conduit trench and minimizing bedrock removal. Additionally, custom equipment, including a specially designed excavator undercarriage and a gantry crane, facilitated the installation of the wider, heavier boxes in a self-performed Support Of Excavation (SOE) system.
The project’s base bid included 3,150 linear feet of 8-foot x 10-foot box culvert and 620 linear feet of 8-foot x 12-foot box culvert for a total of 3,770’ linear feet of box culvert. After the value engineering process, the project concluded with 1,689 linear feet of 8-foot x 20-foot box culvert and 2,035 linear feet of 60-inch ADS pipe. The key was the overall length of “deep” box conduit requiring a complex sheet pile cofferdam system was decreased and the remaining storage, in the 60-inch pipe, was able to be installed via conventional methods, due to it being at a shallower depth.
Environmental preservation and safety were top priorities throughout the project, given its high public profile and proximity to Maine's popular Back Cove Trail. Sargent's leadership fostered a culture of safety, mentoring, and continuous improvement among the crew, resulting in a stellar safety record with no recordable or lost-time injuries. The project also benefited from Sargent's history of collaboration with the City of Portland and cooperation with the Portland Water District, leading to additional work involving the replacement of an existing force main.
The project's success garnered widespread attention, both locally and internationally, with coverage in New England Construction magazine, a visit from Maine Governor Janet Mills, and tours attended by various industry associations. Sargent's Back Cove West Storage Conduit project exemplifies excellence in construction and teamwork, reflecting the company's commitment to innovation and delivering exceptional results.

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Innovative problem solvers, well done!
Sargent Corporation is a team of over 425 employee-owners, building infrastructure including renewable energy projects, highways, commercial site work, landfill cells, highways, and underground work in the Northeast US and Mid-Atlantic region.
Sargent has a rich, near-century-long history and continues to focus on preparing the next generation leading into its second century.