High Falls Gatehouse Replacement

An In-depth Project Overview

This project aimed to fabricate and install a Steel Cellular Cofferdam in front of the High Falls Gatehouse. This endeavour was vital to allow for the demolition and subsequent replacement of the gatehouse under dry conditions. In addition, the project encapsulated the setting up of a new micropile at the substation near the Generation Station. The project’s vast scope covered an array of operations, including barging, hoisting, craning from various terrains, sheet piling, and underwater diver work, among others. The unique construction of the cellular cofferdam extended across the river, tying the edges of both shores through a rectangular cell system. A large circular cellular cofferdam stood in the river, ingeniously designed to withstand the powerful river currents and facilitate construction vehicles and equipment to access the dry side.

Background: Understanding the Need

Central to the project was constructing rock-socketed and rock-anchored steel spud piles. These were post-tensioned, serving as the foundational pillars of the cell. Over these spuds, an engineered structural steel frame was established, thereby shaping the cellular cofferdam’s frame. Following this, steel sheet piles were set up on both sides of the cofferdam, extending to the river’s bottom. Their primary role was to encircle the cell structure and prevent water from seeping. Once the sheet piles were in place, the riverbed was dredged, revealing the bedrock. Then, tremie concrete was meticulously poured to seal the bottom of the structure. To complement the dam’s structure, a new substation building was proposed, anchored by newly installed micropiles, ensuring a robust foundation.

Final Thoughts and Reflections

The project’s complexity was further emphasized as all cofferdam-related tasks were executed from barges on the water, positioned right in front of the existing High Falls Gatehouse/Generating Station. Given the project’s magnitude and its environmental sensitivities, robust environmental protection measures, quality control protocols, and safety regulations were strictly adhered to.  The decision to undertake the project during the cooler months of Fall and Winter further showcased the team’s foresight and commitment to ensuring the least disruption to the environment and the local ecosystem. This project is a testament to modern engineering’s capabilities and possibilities when combined with meticulous planning, state-of-the-art techniques, and an unwavering commitment to quality and safety.




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