Efficient, Economical Grout Solution For Downers Grove

Reducing Sewer Line I/I With Grouting Allows Sanitary District To Avoid Major Expense
April 2014, Vol. 69 No. 4

To counter these stresses, sanitary districts such as DGSD regularly inspect sewer systems and make repairs to replace damaged pipes and control I/I levels to enable the system to function as designed. DGSD, for example, annually cleans 25 percent of its sewer pipes and sets a goal of conducting televised inspection of 10 percent of the system. It has also conducted continuous flow-metering of the system since 1996.

Grouting decision

The three primary goals of the 2009 project were to reduce the I/I that in extreme cases increased the system’s flow to 10 times its average daily flows, to extend the life of its pipes and to reduce maintenance demands on the District’s crews. Of the various techniques of repairing sewer lines that were possible – open-cut replacement and repair, cured-in-place pipe (CIPP), various pipe lining methods and chemical grouting – the latter involves the newest technology and is perhaps the least well understood. DGSD, however, had used chemical grouting on previous rehabilitation projects with reasonable success in terms of I/I reduction. In addition, 96 percent of those grouted pipes that had been grouted were still passing inspection five years later.

“Our previous experience indicated to us that chemical grouting was a viable, cost-effective solution to reduce I/I,” says Bob Swirsky, DGSD’s sewer system maintenance supervisor. He points out that – in areas where it is an appropriate solution – using chemical grouting enables DGSD to avoid the dramatically more expensive repair options.

For this project, DGSD identified particular areas where pipe conditions were optimum for grouting – i.e. areas where its televised inspections had found no severe pipe misalignment or failure.

Chemical grouting is the pressure injection of a multiple-component chemical material into and through leaking pipe joints to seal the joint and prevent I/I. It also stabilizes the soil around the joint, helping to prevent future pipe movement and I/I.

Before chemical grouting begins, pipes are thoroughly inspected and cleaned of grit and root intrusions. If inspections show that pipes are leaking but stable, or are less stable but not yet to the point of failure, grouting is a viable solution. Beyond that, intrusive structural repair will be needed. The cost of those extreme measures can be as much as 10 times the cost of grouting.