Zoyda Boisvert — Chemical Grouting: A Solution to Infiltration

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Chemical Grouting: A Solution to Infiltration

Editor’s Note: We want to thank Avanti International for permission to use their photo as Figure 1 in this post.

Infiltration is defined as an excess of unwanted water entering a sanitary wastewater system from groundwater or storm water. More specifically, infiltration occurs when groundwater enters the sanitary sewer through defects in pipes and manholes (Figure 1). This excess water can cause damage to the collection system when sewers are forced to transport more flow than they are designed to handle. Increased effluent also raises wastewater treatment costs because the facility must treat harmless storm water and groundwater with the sewage. This added flow increases wear on equipment, electrical cost, and overall operation and maintenance expenses. In addition, if the capacity of the collection system or treatment plant is exceeded, untreated wastewater may be discharged into the environment.

Figure 1. Potential Sources for Infiltration

As with most utility problems, there are many potential solutions. For infiltration where defects are localized, some of these solutions include mechanical point repair, injection methods, or rerounding. A discussion of the chemical grout injection option is given below.

The chemicals used for grouting have been available since the early 1960s. They are usually urethane based and when they come in contact with water react to form a polymer material that is a barrier to water flow. The conditions/steps required for grouting are:

A pipe or joint cannot be failing structurally

There must be a path for the grouting solution to flow out into the soil

The area must be free of debris such as roots, grease and other obstacles that may prevent proper application of the grout.

Application of the chemicals at a pressure higher than the water table of inflowing water.

Final testing of the repair (air pressure or visually).