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Flood Grouting

In the flood grouting method, a section of sewer system consisting of a mainline between two manholes, the manholes themselves and the laterals that connect to that mainline is sealed using a sequential flooding operation. First, the pipes within the section are cleaned and the section to be grouted is isolated using plugs from the rest of the sewer system and from the adjacent buildings at their connection to their lateral. Then, a first solution comprising the main chemical grout (a sodium silicate based solution) is pumped into the section until the manholes are filled. The hydrostatic pressure will cause the grout to flow out of the pipe/manhole system wherever there is a defect susceptible to leakage. Next, the first solution is rapidly pumped out – leaving the defects and the surrounding soil saturated with the solution. The sewer section is then refilled with a second chemical solution, which reacts with the first quickly forming a concrete-like matrix that binds and consolidates the ground around the defects. After the completion of the reaction of the two chemical solutions, the second solution is pumped out. The sewer is then flushed to remove any excess grout, the seals are removed, and the sewer section is returned to service. With effective fluids management, it is possible to reuse some of the unused portions of each solution in subsequent flood grouting operations.