The failure of parallel sanitary sewers located in the environmentally and culturally sensitive Shoreline Trail Park at the east end of the Burrard Inlet, in Port Moody, British Columbia would have been a disaster.
Luckily, the leadership in Port Moody is proactive and have long insisted on maintaining a robust condition assessment program. This allows them to better identify and plan out work, so catastrophes like this don’t happen.
Such was the case in 2019 when the Port Moody Shoreline Trail Sanitary Sewer Upgrades Project first began to take shape. The project involved the rehabilitation of the existing force main – a 600-mm diameter DR41 PVC sewer built in 1988 to service the Imperial Oil Co. lands – and a 400-mm asbestos cement gravity sewer installed in 1970 that runs parallel to the siphon along the Shoreline Trail.
The forcemain collects approximately 250 litres per second during peak wet weather flows and discharges into Metro Vancouver’s Coquitlam Interceptor at Dewdney Trunk Road. The gravity sewer collects approximately 24 litres per second during peak wet weather flow and discharges to Metro Vancouver’s Port Moody Pump Station on Murray Street.
The two sewers run through the park below a paved multiuse pathway and through sections of forested land. Within the alignment the sewers cross five watercourses, two of which are salmon bearing, and through a Great Blue Heron rookery situated above a wetland.
Shoreline Trail Park is bounded by Burrard Inlet and the Canadian Pacific Rail right of way. These bounds impose both physical and environmental constraints impacting the designs available for rehabilitation of the infrastructure.
Considering Trenchless Methods
The City retained Burnaby-based Kerr Wood Leidal (KWL) in 2019 to serve as the design engineer and contract administrator for the project. From 2020-2021, KWL worked on the design of the project, which included looking at multiple options including open-cut replacement of the sewers, sliplining, pipe bursting and cured-in-place pipe (CIPP) relining.
Though it appeared that CIPP would be the best alternative, Port Moody had some concerns about the use vs. using other options. This concern was despite the City’s familiarity with the process having used it before.
“The City had some concerns about the overall expected lifespan of a CIPP lined pipe when compared to an open-cut install,” says Sam Eichenberger, P.Eng., project engineer, KWL. “We responded that CIPP has a similar theoretical shorter life expectancy to new pipe due to a reduction in QC due to the underground installation. The City determined the potential reduction in overall life was preferred when compared to the disruption of open-cut installation.”
After thorough consideration, the City and KWL concluded that CIPP was the frontrunner for both pipelines.
Some of the factors in making this decision included:
- Environmentally Sensitive Riparian Areas: The sewers cross eight watercourses and riparian areas where with federal restrictions for any work within 30 m of the watercourse outside of the fish window that runs from the beginning of August to the middle of September each year.
- Great Blue Heron Colony: A Great Blue Heron colony adjacent to the path results in construction related restrictions on tree impacts and the timing of construction from Jan. 15 to Sept. 15.
- Pressure Sewers Elevations: Ensure no backflow from the forcemain into gravity feeder sewers.
- Canadian Pacific Rail Right of Way: Limited work areas and access to site.
- Archeological Material: Existing known archeologically significant sites within or near the project area, and potential new areas.
- Forested Areas: Trees in this area have a high ecological and community value and efforts to limit tree impacts constrained the design in most locations.
“CIPP provided the most flexibility for placement of the access pits and the least number of access pits when compared to other trenchless methods. This allowed for maximizing tree protection and avoidance of work within environmentally sensitive areas surrounding watercourses,” says Eichenberger. “The use of CIPP also provided better hydraulics for this particular sewer when compared to sliplining, which would reduce the inner diameter by too much. The vast reduction in excavation for CIPP compared to other methods was expected to reduce the archaeological impacts of the project in an area with known village sites.”
The Team Contracting Approach
With a plan in-hand, the Shoreline Trail Sanitary Sewer Upgrades Project was put to tender with Surrey-based PW Trenchless and Edmonton, Alberta-based Insituform Technologies Ltd. teaming to complete the work. PW Trenchless’ scope as the prime contractor included all site preparation, bypassing, restoration and permanent structures installation for future bypassing. Insituform Technologies handled the CIPP portion of the contract.
A key consideration in planning the project was balancing the requirements of the main work components: force main lining required constructing bypass, excavation of pits, cleaning, setting up installation sites and liner installation; gravity sewer lining required access to manholes adjacent to the paved trail. These tasks required specific equipment that had to share the trail itself, and the limited access resulting from the CP Rail tracks.
All work was planned to meet the owner’s set guidelines, minimizing impact to trees, great blue herons, archaeological conditions, and keeping as much of trail as possible open to the 200,000-plus per year.
George Bontus, P.Eng., director of engineering, Insituform Technologies Ltd., notes that PW Trenchless’ experience and local knowledge played a huge role in addressing many of the issues presented by the site conditions. “A significant factor in smoothing the lining component of the work was their decision to install a full-length bypass, opposed to the suggested method of bypassing in stages, which would have resulted in a longer lining schedule,” says Bontus. “It also eliminated the need to install temporary and then permanent connections to the existing pump station connections to the forcemain.”
Selecting the Right CIPP
The lining of the asbestos cement sanitary sewer was a straightforward endeavor using steam-cured inverted felt CIPP. It’s the lining of the PVC forcemain that posed the most challenges and required thorough research from the contracting and design teams to ensure the project’s success.
“The contract specifications were based on thermosetting CIPP liners,” says Bontus. “A request was made to consider ultraviolet (UV) liner products, and the city and consultant agreed.” Based on that, Insituform researched the CIPP products available and looked specifically at:
- Felt/long-oriented chop (LOC) fiberglass reinforced tube, installed by inversion and cured with steam or hot water.;
- Felt/random oriented chop (ROC) fiberglass reinforced tube, installed by inversion and cured with steam or hot water.
- Glass fiber (GF) based tube, pulled-in-place and cured with UV light.
- Insituform ultimately decided to use the Saertex Type S+XR liner because it proved to be more cost-effective, with significant reduction in installation setup and improved cure time compared to the epoxy resin systems.
“The UV process significantly reduced the cure time for the liner and reduced the size of the installation package,” says Bontus. “The reduced equipment [on site] resulted in significantly lower impact on trees and the ability to access the site for gravity CIPP installations and even on the PW Trenchless team for opening pits.”
While typically known for its steam-cured, inverted felt, CIPP installations, Insituform Technologies Ltd. has installed UV products on gravity sewers in Ontario and Quebec for several years. However, the Port Moody project is the company’s first use of a UV pressure pipe liner, as well as the first UV pressure pipe installation in a sewer forcemain in North America.
As with any trenchless installation, the project was not without its challenges, the most significant was the liner manufacturing took place in Germany. The oversea shipment led to an increased shipping time to site.
To help ensure a successful installation, Insituform’s local CIPP crew was augmented with Insituform corporate UV and pressure pipe termination fitting expertise, as well as Saertex MultiCom support onsite.
The forcemain component of the project included 14 installations ranging from 41 to 180 m, requiring 15 access pits. A segment at Noon’s Creek was initially planned to be installed using the ROC liner due to the unknown configuration of the siphon. However, the technical team reviewed the CCTV records for this segment and determined that the UV cure liner would be feasible. The lining team had procured one additional length of UV cure liner to be able to reinstall any of the 13 planned segments should there be an issue with material or installation.
PW Trenchless carefully managed the site and was able to maintain good access for all construction activities over the course of the project.
“Advance planning is key, understanding the many risks on the project. Involving contractor, consultant, suppliers, and other stakeholders in advance can provide opportunity for multiple savings,” says Marcelo Nakashima, PW Trenchless Construction.
Multiple test specimens were retrieved from the end terminations at the liner ends, the intermediate pit, as well as from inside the host pipe termination spool at the intermediate pit to assess liner condition and mechanical properties. These were the most representative samples. The technical team reviewed and assessed the samples and test results, with compliance verification provided by a third-party test lab.
“Having completed the project and seeing the level of disruption provided even from using this trenchless technology it has really hit home how difficult this project would have been had it been completed with open cut installation,” says Eichenberger. “The archaeological, environmental, social, and ESC impacts would have been astounding compared to the impacts we saw through CIPP.”