Fletcher's Creek trunk sewer rehabilitation

2021 Project of the Year Rehabilitation Honorable Mention: Fletcher’s Creek Trunk Sewer Rehabilitation

The 2021 Trenchless Technology Project of the Year Rehabilitation Honorable Mention project is awarded to the Fletcher’s Creek Trunk Sewer Rehabilitation for the Region of Peel in Ontario, Canada.

The  Region of Peel, a Regional municipality in southern Ontario, Canada, consisting of cities of Mississauga, Brampton and the Town of Caledon, provides essential social and infrastructure services to 1.5 million people and more than 175,000 businesses. RCI was retained by the Region to complete condition assessment, detailed design, and contract administration services for the rehabilitation of the Fletcher’s Creek Sanitary Trunk Sewer and associated maintenance holes (MH). The project scope included 41 trunk sewer segments, approximately 4 km (2.5 miles) of 750-mm (36-in.), 975-mm (40-in.), and 1,200-mm (48-in.) in diameter at an average depth of 8 to 12 m (26 to40 ft). Previous condition assessments, conducted by the Region, revealed that several sections were in poor condition, with longitudinal fractures and heavy infiltration. The first phase of this project was to conduct inspection and condition assessment of identified trunk sewer sections; grade according to PACP requirements; assess by overall risk of structural and operational/service defects; and make recommendations for post-inspection monitoring or rehabilitation. The design phase included the recommendation for the identified sewer sections with structural and service deficiencies for rehabilitation with a combination of CIPP lining and mechanical seals. Recommendations for MHs included elimination of infiltration by chemical grouting, replacement of ladders and platforms to comply with Region standards. The goal of the rehabilitation was to restore structural integrity, eliminate infiltration, establish a corrosion barrier for the off-road sewers and extend sewer life for over 50 years. Rehabilitation construction, the final phase of the project, began in August 2020, with all off-road works completed to date (22 CIPP sections – total length of 2.4 km (1.5 miles), 15 installation shots with longest inversion of 1,050 ft). The remainder of the project is scheduled to be completed June 2021.

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Why Project is Outstanding:

Four sewer sections were previously attempted to be CIPP lined in 2006 but failed during construction due to the inability to stop heavy groundwater infiltration by grout sealing. RCI investigated the implications of groundwater on the various CIPP curing methods along with limitations and included the requirement for hot water cure for sewers with high groundwater table. The infiltration gushers were also required to be sealed by mechanical joint sealing prior to lining. Specification also required utilization of dual continuous temperature monitoring along the invert, in addition to thermocouple temperature monitoring. This provided increased confidence that the installed liners had adequately cured through monitoring and recordable evidence. Due to limited available space for over the hole installation, fiberglass reinforced liners were designed and installed on two 1,200-mm (48-in.) sewer sections (each 200 m (650 ft) in length, 11m (36 ft) in depth) remaining within the limits of site access capability, pushing the boundaries of the technology. Most of the sewers are located within the floodplains with MHs located near the creek, which is home to Redside Dace, an endangered species with its habitat protected under the Endangered Species Act. To minimize disturbance to the habitat, RCI investigated and identified the ability to utilize temporary wood matting over existing trails and grassed areas and specified this as part of RFP requirements. This approach was reviewed by environmental agencies and eliminated the need for additional permitting, which maintained schedule for this critical phase of the project with minimal disturbance to the surrounding environment. The existing trails run behind many private residences and are used heavily year-round. To minimize trail closure extent and duration, the RFP required use of wood matting only within certain areas of the trails. Installation and restoration of these access mats was also quicker. As a result, the surrounding residents and stakeholders were pleased with the minimal disturbance and inconveniences experienced.

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RELATED: Challenging Trunk Sewer Condition Assessment and Rehabilitation Initiatives in the Region of Peel

Project Owner: Regional Municipality of Peel

Engineer: Robinson Consultants

Contractor: LiquiForce

Value of Trenchless Project (US$): $10.5 million

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