Project Description
Robinson Consultants Inc. was retained by the Region of Peel to complete the detailed condition assessment, detailed design (including supporting preliminary and technical reviews, memos and studies), and contract administration and site inspection for the rehabilitation of the Fletcher’s Creek Sanitary Trunk Sewer. Project scope included 41 maintenance hole to maintenance hole segments, approximately 4km of 750mm, 975mm, and 1200mm in diameter at an average depth of 8-10m. The project also included the rehabilitation of maintenance holes and appurtenances for Fletcher’s Meadows within the City of Brampton.
The 2013 and 2017 detailed condition assessment of the Fletcher’s Creek Sanitary Trunk Sewer, conducted by the Region of Peel, revealed that several locations of the sewer were in poor condition, with longitudinal fractures and heavy infiltration, as well as several maintenance holes requiring 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 maintenance holes included elimination of infiltration via chemical grouting, replacement of ladders and platforms to comply with Region of Peel standards and repair interior appurtenances as required.
Robinson Consultants Inc. also assisted with the pre-construction and construction phases on the project involving working with the Region of Peel’s procurement team on the preparation of a Request for Proposal (RFP) including evaluation criteria, technical specifications, and engineering drawings to select a successful contractor for construction. contract administration, site inspection, and quality control services were completed during construction.
Engineering Innovation
Due to the overall size and complexities of the project, the Region of Peel required a strong procurement document that allowed for a fair bid process, which clearly articulated Region’s requirements. It was crucial that the document also ensured that the selected Contractor was qualified to complete the project and had proposed a sound, detailed approach and methodology. The document had a strong focus on the overall project deliverables, evaluation criteria, and rigorous technical specifications for QA/QC throughout the project.
Robinson Consultants Inc. investigated the implications of ground water on the various CIPP curing methods along with limitations and included the requirement for hot water cure only for applicable segments with high groundwater table and longer installation shots. The specification also required the utilization of a dual temperature monitoring system along the invert, in addition to standard temperature monitoring at the maintenance holes. This provided stronger accountability on the contractor to install compliant CIPP liners through recordable evidence of a fully cured CIPP liner.
Four sewer segments were attempted to be CIPP lined in 2005 but initially failed likely due to excessive groundwater pressure experienced during installation and curing. This required installation of a second liner over the existing liners shortly after the first liner was installed. In order to eliminate the greater risk of a Contractor’s inability to stop groundwater infiltration in advance of liner installation, the requirement to eliminate gushing infiltration by installing mechanical seals was included in the RFP. This greatly reduced the risk of chemical grouting not providing sufficient resistance to hydrostatic pressure exerted during liner installation and curing.
Public Consultation and Stakeholder Engagement
A majority of the sewer segments are located within the Fletcher’s Creek Floodplains with access maintenance holes located in proximity to the Creek. Fletcher’s Creek is home to Redside Dace which is an endangered species with its habitat protected under the Endangered Species Act. Excavation activity associated with construction of a temporary access road within the Floodplains of Fletcher’s Creek would have required extensive permitting from the Ministry of the Environment, Conservation, and Parks (MECP). In order to minimize disturbance to the habitat, Robinson Consultants Inc. 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 review by the Credit Valley Conservation (CVC) and MECP and resulted in eliminating the need for additional permitting allowing the execution of the critical phase of the project on time with minimal disturbance to the surrounding thus protecting the environment.
Further stakeholder co-ordination was required with the City of Brampton, including City Parks and City Traffic groups. This co-ordination was a key to the success of the project to ensure appropriate notifications and scheduling for the closure of the public path through the park and both road closures and lane restriction during construction.
In the News
Challenging Trunk Sewer Condition Assessment and Rehabilitation Initiatives in the Region of Peel
