As infrastructures age, the demand for expensive repairs increase. Failures can cause contamination, lead to sinkholes or roadway damage. Sliplining is a common upgrade for an aging septic infrastructure. Common for septic pipes, a new carrier pipe is installed within the original host pipe. Flow is transitioned into the new carrier pipe abandoning the old host pipe. Between the two pipes is a void space. This annular space is still susceptible to water filtration,
cave-ins, and root growth. Left untreated, this space can pose as a risk to the new carrier pipe or the supported roadway above. Filling and sealing the annular space is an important step to extending the life of the newly revived infrastructure and surroundings.
Fall of 2022, an installer contacted the Engineering Support Program at FillRite Technologies to discuss the benefits of using a light weight foam to fill this annular space. Their client was evaluating the use of CDF (Controlled Density Fill). Unfortunately CDF was heavy and would not seal and protect the exterior of the new carrier pipe. Additionally, delivery of the product in the congested work zone would be difficult. Lightweight FillFoam could be installed quickly from port to port offering a complete void fill.
Located in Western Canada, this annular space encompassed nearly one mile of sliplined septic pipe that required void filling. The void space was between the nearly 5 ft diameter host pipe and the newly installed carrier pipe that measured just over 4 ft in diameter. The sections to be filled varied in distance from 200-400 feet long, commonly from manhole to manhole. Each section required a pumping point and a vent point. Traffic control was utilized to close down one lane with minimal disruption to traffic. Accommodation were made to continue operations despite the cold winter temperatures and snow. Containment areas with a hydro-vac extracted any waste water displaced from the pipe during foam installation.
Various densities of FillFoam were installed into the annular space and pushed forward or backfilled. High density foam was used to travel further distances while lower density foams could be used for shorter
distances or smaller voids. Throughout the project samples were retained to verify density and yields.
Over multiple mobilizations, the contractor installed nearly 300,000 pounds of FillFoam material into the annular space. Materials were shipped via totes in concentrate within 8 truckloads. A volume of over 1,000 cubic yards of FillFoam foam was produced onsite at a rate of nearly 30 cubic yards per hour. Had the contractor decided to install
CDF, over 100 truckloads of material weighing over 40,000 pounds each would have been required. For months trucks would have needed to navigate the congested downtown area further disrupting traffic and causing additional strain on the road.