Annacis Island WWTP is undergoing a range of improvements, including replacing the equipment inside the trickling filters. But first, the massive dome atop a trickling filter – the size of an Olympic-sized pool weighing 30 full size vehicles – has to be removed.
[Narrator] The four domes at the Annacis Island wastewater treatment plant are a familiar sight to anyone driving over the Alex Fraser Bridge. These buildings are called trickling filters. In spring 2020, one of those domes had to be removed.
[Kienan Hamm, Project Manager, Maple Reinders Constructors Ltd.] So on April 29th, we had the removal of the trickling filter number one dome. The lift of the dome was part of the refurbishment project for rehabilitating and refurbishing the trickling filter after its initial 25-year lifespan.
[Narrator] The trickling filter contains equipment that uses a biological method of removing organic materials from wastewater. Replacing the large equipment meant having to remove the roof.
[Jacqueline Liu-Pope, Senior Project Engineer, Liquid Waste, Metro Vancouver] It is the first time that we are removing the roof. The last time the roofs actually got moved was when they were being installed back in the late 90s.
[Narrator] Lifting such a large structure is challenging on several fronts. To help ensure success, some of the dome’s triangular panels were removed in advance.
[Kienan Hamm] But the diameter of the dome is similar to like an Olympic-size swimming pool and the weight of the dome is comparable to about 30 full-size vehicles. To do a lift that’s complicated like this, wind plays a huge factor because of the surface area of the dome. You could have huge safety risks if the dome started swinging and counterbalanced that crane to the point where it was outside its safe lifting radius. So engineers did a critical lift plan prior to the lift of the lid and determined the percentage of the surface area that needed to be removed so that we had a safe lifting capacity. We are giving the limit of roughly six kilometres an hour wind speed tops in order to remove the dome.
[Narrator] After the dome was successfully lifted, work began to refurbish the trickling filter and assess the dome’s panels.
[Kienan Hamm] Because after the dome was removed, it was determined by the engineer that the panels needed to be replaced. They’re replacing those panels with a brush-blasted aluminium so that there isn’t a reflective property to make sure that driving over the Alex Fraser Bridge is safe.
[Jacqueline Liu-Pope] The plan is to refurbish one trickling filter a year. That would take us to 2023 when all four trickling filters have been refurbished. And there’s plan to build two more after the next expansion project.
Learn more about the improvements at the Annacis Island Wastewater Treatment Plant.