Successful Sanitary Sewer Main Replacement with the Help of Chemical Grouts

Written by Jessica Williams on . Posted in WCQ Newsletter


Midwest Mole is a leader in the trenchless technology industry and has been in the tunneling industry for over 30 years. They offer a broad range of underground services to municipal, utility, highway, railroad, and the private sector. Some of their services offered are Auger Boring, Pipe Ramming, Handmining, Slip-Lining, Cellular Grouting and Microtunneling.


When the need for the replacement of a sanitary sewer main in Newport News, Virginia arose, Midwest Mole and their experienced team were called into action. The new sewer main, located near a public roadway, is a 30-inch ductile sewer main in 48-inch casing with a crossing length of 181 feet. Most sanitary sewer mains are located within public right-of- ways. However, the challenge in this situation was the sanitary sewer main being situated in unstable soils. Advancement of the TBM could possibly depressurize the ground resulting in settlement and subsequent damage to the surface infrastructure, both inside and out of the public right-of-way. To stabilize the ground, Mr. Brian Liotti, Project Engineer, of Midwest Mole discussed with Britt Babcock of Avanti to determine which product would best stabilize the soils surrounding the TBM. After discussing which grout to use and the appropriate installation technique for the situation, Avanti’s AV-275 Soilgrout was selected. AV-275 is a very low viscosity, single component, hydrophobic polyurethane resin that uses moisture as an initiator. AV-275 is designed to bind together, waterproof loose granular soils, and form a dense, impermeable semi-rigid foam.

The AV-275 was injected through the steel face of the launch shaft’s steel liner into the soils. The goal was to cutoff potential water inflows which could result in destabilization of the surrounding soils once the 6-foot diameter break-out hole was cut from the steel liner. This would allow the TBM to move forward into the launch shaft for dismantling and lift out. AV-275 successfully permeated the silty sand, stabilizing the soil and creating an effective water barrier preventing the launch shaft from flooding.

Direct from the contractor: “Just wanted to let you know we were very pleased with the AV-275. After we cut open and exposed the face, it looked as if the product “spidered” throughout the ground and made for a solid face.”

Congratulations to Brian Liotti and his team at Midwest Mole for completing another successful project!

Reference: Midwest Mole
Mr. Brian Liotti, Project Engineer
6814 West 350 N
Greenfield, IN 46140
(317) 545-1335