Innovative trenchless technology solution used by proactive municipality
At a glance
Traditional sewer line replacement methods are costly and often require clear-cutting into precious environmentally sensitive land. GHD wastewater engineers worked with the City of Cambridge (the City), Ontario, to implement an innovative trenchless technology solution for the forty-five-year-old Hespeler trunk sanitary sewer line.
The challenge
The City of Cambridge is responsible for the operation and maintenance of the Hespeler Trunk Sanitary Sewer. This project consisted of the structural rehabilitation of one-thousand-sixty-nine meters of six-hundred-millimeter diameter, three-hundred-ten meters of six-hundred-seventy-five-millimeter diameter and sixteen sanitary maintenance holes.
The sewer line conveys wastewater from north Hespeler under the Speed River to the Hespeler Wastewater Treatment Plant, servicing over thirty-five-thousand residents within the local community. The City’s asset management department routinely inspects the sewer by using a closed-circuit television camera. This proactive inspection approach illuminated points of serious concern including structural and maintenance defects, infiltration, and inflow.
Our response
GHD prepared a feasibility report that evaluated a series of four separate rehabilitation options for the aging sewer system. CIPP was selected as the preferred construction technique due to its multiple benefits, which included reduced environmental impacts (no excavation, less dewatering requirements, reduced greenhouse gas emissions and minimal vegetation removal), the ability to meet all technical requirements, the ease and speed of constructability, reduced impacts on the built and social environments, and cost advantages.
Traditional replacement methods would have resulted in significant costs and approval challenges for the City, including the requirement to cut the surrounding forestry within an environmentally sensitive area to provide adequate access and laydown area needed for construction. Greater lead-time would have been required to secure approvals from the Ministry of Natural Resources and Department of Fisheries and Oceans for the crossing of the Speed River, and fill alterations permits from the Grand River Conservation Authority. In addition, the City was concerned about the risks of operating a collection system in a compromised state of service.
The impact
The use of CIPP in larger diameter sewer rehabilitation projects is often perceived by the industry as being expensive because of the requirement for by-pass pumping. By altering the construction procedures and shortening the by-pass duration, the GHD team of engineers prove that large-scale sewer rehabilitation projects that use CIPP are cost effective. The results of the Hespeler trunk sewer line are a cost savings of approximately one-million dollars.
GHD is ranked 15th of the Top Fifty Trenchless Design Firms in NA, by Trenchless Technology magazine, 2017.
Outcome
- Rehabilitated one-mile-long, twenty-four and twenty-seven-inch diameter trunk sewer using cured-in-place pipe (CIPP)
- Extended service life of sewer line for approximately fifty years
- Saved the City of Cambridge one-million dollars
- Protected the local environmentally sensitive land regulated by the local Grand River Conservation Authority
- City of Cambridge, Ontario, nominated the project for Rehabilitation Sewer Project of the Year Award, 2018
- Recipient of the prestigious Award of Excellence from the Center for Advancement of Trenchless Technology (CATT), 2018: Project category.