Robinson Consultants Inc. (RCI) was retained by Niagara Region to complete the rehabilitation of the Stamford Interceptor Trunk Sewer (SITS) Phase II in the City of Niagara Falls.
The Region identified the need to rehab the SITS based on historical CCTV inspections which showed the segments in very poor condition based on severe corrosion and exposed reinforcement due to H2S in the pipe. The project included 1,560 m of 1,050-mm diameter reinforced concrete pipe, composed of 14 segments and 14 manholes. The SITS runs parallel to the Ontario Power Generation (OPG) canal and along a new high-traffic pedestrian trail.
A rehab technology analysis was completed, identifying CIPP as the preferred form of rehab for the sewers and wall-bond spray-applied lining for manhole rehab. Rehab specifications developed included CIPP spec with detailed requirements for the use of hot water cure directly upstream of a wastewater treatment plant (WWTP). This included the treatment of cured water prior to discharge to reduce the styrene concentration prior to reaching the WWTP.
Key constructability considerations for this project included coordination with the local stakeholders due to the sewer being in the Region’s easement.
The project also included the need to address the technical challenges with lining a significantly deteriorated sewer due to H2S, including risk of collapse during cleaning and enlarged internal diameter. The project also had unique constructability review due to the final downstream sewer segment finishing inside the Region’s WWTP. This review required consideration of the ability of the liner tail to enter the facility and the ability of the bypass to discharge into the facility.
RCI completed the development of a negotiated request for proposal (NRFP), including spec, special provisions, Niagara Peninsula Standards references and drawings. Engineering drawings were developed to provide the general plan and profile of the sewer with an aerial overlay for the treed portions of the alignment and the location of utilities to provide for Contractors to plan the location of buried bypass pipe at road crossings and the location of overhead wires along the alignment. This NRFP is only the second of its kind that RCI is aware of in this market, the first being issued by the City of Toronto’s Sewer Rehab Program that RCI also managed. The process involves three stages: price per point evaluation, best and final offer (BAFO), and final contract negotiations with the top proponent.
Why Project Is Outstanding:
This project involved the unique technical challenge of lining a deteriorated sewer (due to H2S) at risk of collapse during cleaning and enlarged internal diameter. There were also complexities associated with lining the final downstream sewer segment inside the Region’s WWTP.
Not only did a sewer segment culminate inside a WWTP, but other sewer segments were located under the Millennium Recreational Trail (MRT) and in the Region’s easement in OPG lands. Interaction and cooperation with stakeholders and the public was required to minimize disruption of trail use, and coordination with OPG was required for access to the property, construction of temporary access roads, and security during construction. Use of CIPP also reduced overall closure times and disruption to the MRT, and mitigated impacts to OPG land.
Environmental impacts are always a top concern. The small amount of styrene condensate that is produced during curing was a concern during design as the styrene in the discharge water can impact wastewater treatment, including digestive bugs in the secondary system. The contract required the Contractor to have a plan to capture all styrene condensate/discharge during curing. The contractor pumped the condensate into totes located at the inversion or tail manhole depending on the direction of the installation. A temporary frac tank and CCG-1000T carbon filter was installed near the main bypass discharge point and the condensate water was transported to the frac tank for temporary discharge. After the lining was complete, the captured condensate was tested for styrene, which read as 2,800 µg/L. It was circulated through the carbon filter until the concentration was lowered to 0.3µg/L, well below the specified limit in the contract. The final condensate, after styrene removal, was discharged into the sanitary system. The contractor also installed a berm approximately 6 to 8 ft downstream of the inlet pipe into the plant. The final inversion into the plant was completed over felt and waterproof tarp so that any residual resin run-off was captured. Erosion and sediment control measures including silt fencing was also installed around the access roads.
The NRFP procurement method allowed for multiple stages of negotiations between the Region and top proponent to discuss their constructability approach, address concerns, and allow the Contractor to propose additional solutions that weren’t prescribed in the contract.
Engineers: Robinson Consultants Inc.
Contractor: Liquiforce (prime contractor)
Subontractors: Insituform Technologies Ltd. , Empipe Sewer Solutions Ltd. , Provincial Construction and Atlas Dewatering Inc.
Value of Trenchless Project (US$): $4,670,000