Groundwater infiltration of sewer pipes is a common problem encountered by municipalities, especially those with aging infrastructure.Among the options available to repair sewer pipe leakage, chemical grouting remains a popular and effective method of stopping leaks and repairing joints without resorting to a full-scale re-lining operation.
“Chemical grouting is a mature technology that stands on its own or complements various methods of trenchless pipe or sewer structure repair,” states a white paper published by the Infiltration Control Grouting Association (ICGA).The U.S.-based group is a division of the National Association of Sewer Service Companies, whose members include suppliers,contractors,engineers and public works representatives.
The paper goes on to say that, “When applied properly and used in appropriate conditions, chemical grouting is a long-lasting, cost effective solution that stops infiltration caused by leaks and failing joints, and helps prevent structural damage from developing in leaking pipe that is otherwise sound. As such, chemical grouting should be incorporated into nearly all wastewater maintenance and rehabilitation programs.”
What is chemical grouting?
The chemicals used to repair underground wastewater pipes were first developed in the 1950s and ‘60s. Urethane grouts reacted with water and moist soil to form rubber-like balls that filled external voids or acted like gaskets in leaky joints.
According to ICGA, the technology was attractive because it was relatively inexpensive,easy to apply, and used non-toxic chemicals that did not cause problems in wastewater treatment plants.
At the same time, low-viscosity “solution grouts” were developed that could be applied using remote-controlled “packers.”Packers are inflatable plugs that isolate short sections of underground pipe so that grouts can be pumped into the section and forced through leaks and failing joints into the surrounding soil. Thus, chemical grouting became one of the first trenchless pipe rehabilitation solutions.While resinous, urethane-based grouts are used to repair leaky manholes, by far the majority of chemical grouts nowadays are used in a water solution, applied bytruck-mounted systems, according to ICGA. Packers can chemically-grout sewer mains up to 144 inches in diameter, while specialized packers can grout laterals up to around 30 feet from the main line.