By Cheryl Mah
Wastewater treatment plants are important municipal infrastructure assets for safeguarding public health and keeping waterways clean. For more than 50 years, the Iona Island Wastewater Treatment Plant (WWTP) has provided primary wastewater treatment to Vancouver, the University Endowment Lands, and parts of Burnaby and Richmond.
The plant has undergone a number of expansions and upgrades over the years to improve wastewater treatment and to meet the demands of a growing population. To comply with federal regulations, the plant is scheduled to undergo a major upgrade to secondary treatment by 2030. For the plant to continue providing effective and reliable service until then, an upgrade to the solids handling processes was required.
Because the area serviced by the plant has a large number of combined sewers, a significant amount of storm water from road drainage is treated at the plant. The Iona Island WWTP solids handling upgrade involved the construction of a new solids handling facility with screening and de-gritting equipment to better remove more of the sand and debris from the liquid waste stream.
When wastewater comes into the plant, it is treated to reduce solids and organic matter content. The new screening and degrit processes remove the inorganic solids (rags, debris, grit) and leaves behind the organic solids of the primary sludge to be digested. This provides for better treatment efficacy in the digesters, increases hydraulic and solids capacity and reduces maintenance of the digesters and associated pumps.
Trotter & Morton Building Technologies Inc. installed and supplied all the mechanical equipment for the project, which included grit separators, screens, new pipelines and a multitude of pumps. The project consisted of upgrades to the existing plant and new construction of a gravity thickener, main pump house and grit separation building. The project required more than 21,000 manhours with an average crew size of 12. Trotter & Morton completed the 18-month project in April 2017.
Working within an operational wastewater treatment plant was the main challenge, according to Mike Lee, the project manager for Trotter & Morton Building Technologies.
“Working at height over the tanks in the existing building was quite dangerous so we had to create a scaffolding system to install the new pipe,” he says, explaining the scaffolding was moved along with the use of a 120 tonne Leibherr crane with a swing-out-jib as the new pipes were installed. “We had to run pipe in the existing plant to tie into the new facilities.”
Limited site access to existing buildings required pipe to be fabricated offsite (using CADMakers) before they were shipped to site for installation. The hazardous plant environment with potential exposure to biological dangers also meant careful health and safety coordination for workers.
Other challenges included multiple projects running concurrently with other contractors, multiple shutdowns to coordinate tie-ins to the existing system, meeting stringent specifications and procurement of equipment with American suppliers.
“Right after we got the job, the Canadian dollar plummeted so we had to really negotiate with the suppliers on the cost of the equipment,” says Lee, estimating value of equipment installed at $2 million.
The successful completion of the $8.6 million project earned Trotter & Morton a 2017 VRCA Silver Award of Excellence in the mechanical contractor category. Kenaidan Construction was general contractor.
“It’s always nice to be recognized by your peers,” says Lee, who is proud of the workmanship on the project. “This project wasn’t our usual HVAC and plumbing work so the crews enjoyed that.”
Lee credits the success of the project to a good project team, “We had a good working relationship with CH2M Hill and Metro Vancouver. The job was difficult but everyone worked well together.”
The latest upgrade to the second largest wastewater treatment plant in Metro Vancouver will help to extend the operational capacity of the plant to the year 2030.
Cheryl Mah is managing editor of MCABC Plumbing & Mechanical magazine.