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:

1. A pipe or joint cannot be failing structurally
2. There must be a path for the grouting solution to flow out into the soil
3. The area must be free of debris such as roots, grease and other obstacles that may prevent proper application of the grout.
4. Application of the chemicals at a pressure higher than the water table of inflowing water.
5. Final testing of the repair (air pressure or visually).

A video providing an overview of this process using remotely operated equipment is given below.

Chemical grouting can also be applied manually and can stop the leak almost instantly. A video of manual grouting for a leak in sewer wall is shown below. 

In summary, chemical grouting technology for stopping infiltration is attractive because the chemicals are non-toxic to the wastewater treatment plant and can be applied using remote controlled equipment or manually for small localized defects. Chemical grouting is a flexible low cost option for infiltration repairing of sewer mains in addition to sewer laterals.

Featured Video: Green Infrastructure for Small Rural Communities

Last week, we shared videos for educating your consumers in ways to improve stormwater quality and increase infiltration. But maybe you're interested in these topics as well. In that case, this week's video is for you. This hour-long webinar recording highlights green infrastructure efforts taken on by two small, rural communities. Representatives from the utilities in those communities discuss reasons why they wanted to take on stormwater management, reasons why they chose green infrastructure, the projects and programs they implemented, lessons learned, and project funding. It includes before and after and process images, but is not a highly detailed build guide.

Featured Video: Freddy the Fish

If April showers have arrived at your utility, then stormwater topics are probably at the forefront of your mind---and your customers' minds too. This makes it a great moment for public education. There are things utilities can do to mitigate stormwater quality, but nothing works quite as well as having your community pitch in to clean up the watershed. This week's video presents basic practices that improve stormwater quality, in terms aimed at your youngest consumers. Freddy the Fish focuses on reducing litter, picking up dog poop, and eliminating storm sewer dumping, and combines these messages with animated and live-action video and brief singalongs. The video would be a particularly good fit for presentations to young school-age children, which in turn can be a great way to engage your community.

For more stormwater public outreach materials, search our document database using the category Stormwater and the type Factsheets/Case Studies. You might also be interested in the EPA's video on stormwater (for adults) here.