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Screw heaps are generally created from structural steel. The tremie piling contractors north west method of positioning concrete includes decreasing a pipeline to the base of the excavation, the pipe end at the top of the excavation is linked to a concrete receptacle. The hoper as well as the pipeline are then charged with the wet concrete mix. The pipeline is then slowly raised out of the excavated opening, placing concrete as it goes. During the lifting process, concrete is constantly replenished to the receptacle in order to keep the system totally charged.