GROUND FREEZING WAS SPECIFIED ON the Bergen Point Wastewater Treatment Plant in West Babylon, New York to provide groundwater control and temporary earth support at both launch and receiving shafts. This was preferred to the other options available which included freezing, diaphragm slurry walls and secant piles. The excavated diameter of the launching shaft was 9.1m to a depth of 38.75m. Designing a ground freezing system brought two unique challenges. The most significant was the absence of; confining layer at the shaft invert, which would result in vertical groundwater flow into the shaft during excavation and complete bottom instability, leading to basal failure. The second challenge was the potential existence of lateral qroundwater flow exceeding one metre/ day. High groundwater velocity can retard and in some cases prevent the formation of a frozen earth structure.
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