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Grouting is a trenchless construction method used to stop leaks in sewer pipes and maintenance access holes without having to do more complex and costly structural repairs. It is effective in repairing leaky pipes and joints, sealing small cracks, and filling voids in the soil outside of pipes.

A leaky sewer pipe can contaminate the surrounding ground with its contents. Groundwater and fine sand and soil particles can also enter pipes through cracks and holes, building up over time and creating blockages in the system.

Grouting involves drilling holes in the general area of the pipe wall leakage. From inside the pipe, crews inject grout through the drilled holes into the surrounding soil. As the grout spreads and hardens, it stabilizes the soil and forms a watertight seal outside the pipe. Crews then plug the drilled holes to form a tight seal inside the pipe.

The type of grout, equipment, injection pressure, and techniques used can vary significantly from project to project.

Depending on the location, depth, diameter, and other features of the sewer pipe or maintenance access hole to be repaired, crews may do the grouting work manually from inside the pipe (as in a large-diameter, deep sewer tunnel), or crews may use a remotely controlled device to do the grouting work (as in a small-diameter, shallow sewer pipe).

Grouting can also be used for the following activities:

  • Sliplining, Tunnel Liner Plates, or Spiral Wound Lining: Fill gaps that exist when a new smaller-diameter pipe is inserted into a leaky larger-diameter pipe. Methods such as Sliplining, Tunnel Liner Plates, and Spiral Wound Lining use grouting to fill the gaps between a liner pipe and an existing pipe or between liner plates and an existing pipe. Grouting the gaps increases the strength of the inner liner pipe and plates.
  • Abandonment of Pipes or Maintenance Access Holes: Fill existing pipes and maintenance access holes that are being abandoned because they no longer serve a purpose in the sewer system. When large pipes and maintenance access holes are no longer needed, filling them with grout can prevent them from collapsing over time and creating voids or other underground problems.

Grouting work involves the following steps:

  • Identify a leak or defect in a pipe or a void (hole) outside a pipe.
  • Perform tests to determine the extent of the leak, defect, or void.
  • Isolate the problem area.
  • Determine a point of entrance to access the leaking pipe, which is usually the nearest maintenance access hole, sewer service lateral pipe, or other connecting line.
  • If necessary, dig an access pit to the required depth to access the leaking pipe.
  • Insert a drilling machine into the point of entrance.
  • Drill grout injection holes through the wall of the leaking pipe.
  • Insert a grouting machine into the point of entrance.
  • Inject grout through the drilled injection holes into the surrounding soil. Let the grout fill the leak in the pipe wall and enter the surrounding soil.
  • Let the grout dry and harden, which will stabilize the soil and form a tight seal outside the pipe.
  • Plug the drilled injection holes to form a tight seal inside the pipe.
  • Conduct tests and inspections to verify a good seal.
  • Backfill any access pit with sand or gravel and apply a temporary asphalt patch.
  • Conduct quality control inspections.
  • Complete permanent pavement restoration of any patched pit after work passes inspection.