Fer-Pal Rehabilitates Critical Watermain in An Environmentally Sensitive Area
Structurally rehabilitating its first watermain with cured-in-place lining (CIPP) in 2002, the City of Toronto has invested in the technology each year since. The City has grown the program to become the largest CIPP lining program in North America, rehabilitating more than 25 miles (40 km) a year.
Historically the City has focussed the program on projects that lay in residential, commercial or industrial areas in the City. One instance of this less traditional location was the rehabilitation of a watermain that had failed under the Mimico Creek in Etobicoke.
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The watermain in need of repair was a 12-in. (300-mm) cast iron watermain that had failed due to a longitudinal crack. This watermain was critical to the surrounding distribution network as it was one of a few to feed the southwest portion of the City. The crack itself had formed in a section located in a bank beside the creek. When the main failed it washed out the surrounding soil and gabion baskets, exposing the watermain to the elements. Due to the severity of the break and location an emergency repair was difficult. Instead the watermain was isolated and shutdown until it could be fully rehabilitated.
Due to the limited access, difficult site conditions and severity of the break the City, along with its consulting engineer WSP, decided that the best solution was to structurally rehabilitate the pipe with CIPP lining. The project was designated as an emergency repair and contracted out to Fer-Pal Construction Ltd. to be completed in July and August of 2018. Aqua-Pipe was selected as the product to be installed.
Before construction could occur, an environmental assessment was required as the area was deemed environmentally sensitive. While some shrubs and bushes required removal, the assessment concluded that several trees (Including Black Walnut and Siberian Elm Trees) could be left unharmed. A large amount of poison ivy located in the area that was required to be removed prior to construction. Once the area was cleared, silt bags and clear stone gravel were stationed around the work area as the location was saturated due to its location. This would prevent further damage to the area while also allowing Fer-Pal to position its equipment accordingly.
Three points of access would be needed in order to properly line the watermain. The first access point was located within an easement at the top of the escarpment on the west side of the creek. The second pit was located approximately 30 ft (9 m) above the second. The last was located 164 ft (50 m) north of the 90-degree bend on the east side of the Mimico Creek walking path. During the time of construction, the walking path that was used for access was closed to the public. This was the only disruption to the public for the length of the project as the surrounding roadway was kept open during construction. As the watermain could be isolated, a temporary above ground bypass was not required.
Once the access pits had be excavated and properly shored, the pipe was cut into and cleaned. The cleaning process including a high pressure flusher as well as a swab that removed the tuberculation from the pipe.
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Following the cleaning, the watermain was inspected via a CCTV inspection. Upon reviewing the video from the line, an unexpected circumferential break was observed underneath the creek as well as the longitudinal crack along the vertical stretch of pipe. Due to the size and location of these breaks it was necessary to address the failures within the watermain in order to ensure consistency and quality during installation. In order to do this, six separate HammerHead Point Repair systems were installed within the watermain. These repairs would prevent infiltration of water as well as ensure the resin used to cure the liner would be contained within the main. Five separate patches were required to seal the elongated crack along the main while a separate sleeve was used to repair the circumferential break underneath the creek.
Upon the installation of the HammerHead Point Repair system, Fer-Pal installed an Aqua-Pipe CIPP liner in two consecutive stretches, curing them using pressurized hot water. Following the curing of the liner it was inspected via CCTV by the City’s consultant before being reinstated, chlorinated and placed back into service. Due to the unique construction of the Aqua-Pipe liner, the finished product would mean a jointless and seamless product stretching from one access pit to the other.
Following the lining of the pipe, the area was cleaned and restored in the sections that were disturbed by construction activity. The last stage of the project was to insulate the area that had been exposed during the original watermain failure. This would ensure the section of the pipe that had been exposed would be protected from elements expected in a Canadian winter. Following the completion of the project the local environmental authority, the Toronto and Region Conservation Authority (TRCA), would be responsible for the reinstallation of erosion controls that were affected during the initial failure.
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The project itself was completed by the first week of September with the watermain being placed back into service within two months of the project start date. What was left in the end was a unique solution to a challenging watermain failure. Other alternatives would have been timely, costly and disruptive to the environment. Instead Fer-Pal was able to breathe new life into a critical watermain, protecting it and the environment around it well into the future.
Geoff Britnell is business development manager (North America) at Fer-Pal Infrastructure.