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

Chemical grouting has several significant advantages over other technologies when the goal is to reduce ground and storm water infiltration. First, the more intrusive repair techniques are solely structural repairs, whereas chemical grouting is an addition to existing stable pipe and actually can also be used as a complementary technology when structural repairs are being done. Structural repairs also require a dry environment in order to be performed. Secondly, while these alternatives are valuable techniques to replace or repair damaged pipes, they do not stop infiltration. Chemical grouting, on the other hand, was specifically developed as a solution for leaking pipes, and being chemical in nature, can be successfully applied in a wet environment.

Another of the advantages of chemical grouting is that the material used can be varied in composition to match the specific requirements of the pipes being grouted. For example, since inspections of DGSD pipe had shown significant root intrusion, after the pipes had been cleaned and roots cut, a chemical growth inhibitor was added to the grout to curtail future root intrusion.

Selecting, grouting the basins

As noted, DGSD has conducted flow-metering of the 149 basins in its system for almost 20 years and has assembled GIS data on pipe condition, peak flows and I/I for each basin. Using this data, Derek Wold, vice president and manager of the Wastewater Group at Baxter Woodman Consulting Engineers, project engineers for the grouting project, and his team worked with DGSD to identify 15 basins that were candidates for grouting.
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Using the 15 years of data, the basins were ranked in severity of I/I by assigning each a number representing the I/I in gallons per minute per lineal foot of sewer per inch of rainfall.
National Power Rodding Corporation (NPR), a Carylon Company, which pioneered the use of chemical grouting and is the nation’s largest chemical grouting group, won the contract to do the grouting of the identified basins. NPR grouted each basin in turn from north to south in the district, using three crews working in each of the basins. That procedure – using three crews in the same basin – allowed DGSD to assign only one inspector to the basin, freeing other personnel for District work.

All lines were cleaned and televised before grouting, allowing the crew to confirm that the lines were acceptable candidates. Before grouting, they removed all roots, mineral deposits and protruding taps from the pipes.