Groat Road and 102 Avenue Relining
Intent of Project
This underground storm sewer system is situated on the west side of Groat Road on the plateau at 102 avenue. The catch-basins pick up the storm water runoff and convey them through a steeply graded 250mm diameter vitrified clay tile pipe within the embankment of the Groat Road Valley to a location with elevation greater than 20m lower where it connects to a collector pipe.
Through previous CCTV inspection(s) the pipe showed several locations with structural defects and corrosion. The risk of a pipe failure was significant and City of Edmonton engineers elected this portion of storm pipe network to be rehabilitated.
As conventional open cut excavation methods, for this site, were undesirable, highly disruptive and extremely costly, the pre-approved trenchless contractors were presented this sewer rehabilitation package for repair proposals.
This underground infrastructure rehabilitation project was unique and posed a number of significant challenges. This The line presented many unconventional and challenging features, including limited and non-conventional pipe access in the downstream end as it did not terminate at a manhole but rather at a tee connection to the side of a 2.4m diameter steeply graded collector line under Groat road.
- The grade was extreme at up to 45%
- Two 60 degree elbow fittings existed within the run length
- There was a material change to corrugated steel pipe which was rough and jagged from corrosion
- Amid-length diameter change existed
- And finally, the pipe presented, at mid-length, fractures and segments missing accompanied by void areas in the bedding adjacent to pipe which rendered it fragile and unstable.
This pipe was not possible to CCTV inspect using conventional self-propelled "Main Line" CCTV camera units as the existence of the 2 said elbow fittings posed excessive risk to the camera getting lodged.
Advanced Trenchless Inc. presented a viable, feasible and cost-effective approach that offered a manageable level of risk. The repair strategy began with pipe preparation and CCTV inspection(s) to verify pipe conditions were as believed. Exact measurements were taken for the placement of the appropriate length, diameter and thickness of CIPP liners.
The intention of the initial stage of rehabilitation was to stabilize the fragile pipe via the installation of a pull-in-place sectional CIPP liner for a total of 6 lineal meters. This liner was placed in position without the visual confirmation of a CCTV camera (since the push-camera did not offer adequate clarity in this 250mm diameter pipe).
This liner was installed successfully without any significant adverse effect to the host pipe. The subsequent CIPP liner was a full length liner that was installed via inversion method. The liner was inserted at the manhole at the upper plateau (102 Avenue) running the length of the pipe through the previously installed sectional liner and ultimately to the tee connection at the 2.4m diameter collector main, a total of approximately 60 lineal meters.
A post installation CCTV inspection was performed to confirm a successful rehabilitation of this high risk, challenging pipe in this scenic area of Edmonton.