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

Of the 24,000 mainline joints tested, 25 percent failed. Each joint required an average of three gallons of grout to achieve a seal. Where inspections detected heavy root intrusion, a root-killing chemical was added to the grout. In one formerly swampy area, where joint failure was almost 100 percent, a diatomaceous earth additive was included to give the grout greater consistency.

Of the 2,100 lateral connections tested, 60 percent failed. Each of these also required an average of three gallons of grout to seal.

Composition, DGSD grouting procedure

The grout used in the DGSD project was an Acrylamide grout complying with ASTM F2304. The procedure used was to seal the joint or lateral being tested and grouted using inflatable socks that isolated it from the main sewer flow. For laterals, the four-foot sock sealed off the lateral joint at the main line and the first one or two joints within the lateral. Following testing, the grout was injected.

After each joint and lateral was grouted, it was retested and inspected to confirm that it was not leaking. Unique to this project, a three-year warranty test is to be conducted after three years of service to ensure that joints are still not leaking. That testing is scheduled to begin in the spring of 2014.

The project originally called for sealing 440 manholes by creating a grout curtain around each structure. After grouting 60 of the manholes, NPR determined that grouting would not be the most cost-effective solution because the backfill around the structures consisted of large rock, and required large amounts of grout to create an adequate curtain. NPR recommended that the manholes be sealed with concrete liners.

“We were originally hesitant to line the manholes, based on past negative experience with both cementitious and epoxy lining” says Swirsky. “In the past we found that unless the surface was cleaned thoroughly and the application carefully supervised, that the surface tended to flake off over time. But given the large amount of grout required to seal each manhole we felt we needed to explore an alternative.

“We asked NPR to complete a demonstration lining on one manhole as a test. They power-washed the surface and used coating much improved over those used in the past, including reinforcement with metal microfibers for added strength. The DGSD inspector on site found the result to be a solid lining and we approved moving forward with the lining procedure for the remaining manholes. In the months since, we have found it to be a satisfactory solution.”