The Capital Regional District’s new Macaulay Point Pump Station is BC’s largest municipal sewage pump station and, with a capacity of 400 MLD, it can fill an Olympic size swimming pool in 9 minutes and is still optimized for daily flows. KWL’s approach turns the traditional pump station design on its head. Rather than designing and selecting pumps for peak flows, we optimized the station for the average daily flows. This approach reduced the overall station footprint, optimized the wet well sizing, reduced the odour control and air management requirements, increased station reliability and redundancy, reduced power consumption, and made the station easier to operate and maintain. Moving forward, large municipal pump stations in BC will be designed differently.

The old station was designed to pump to the deep ocean outfall with a capacity of 150 MLD, causing any excess flows to spill over to a shallow outfall close to a local beach and didn’t have capacity to pump to the new treatment plant. The new station includes more pumping capacity as well as pre-treatment with fine screens and a vortex degritter. A typical station, including the original concept for the station, would have required three 845HP pumping units. Instead, the station was optimized for average daily flows, with more but smaller pumps. The new station includes eight 250HP pumps optimized for conveying daily flows while still providing the capacity to convey peak flows.

Extensive acoustic mitigation, advanced odour control, public amenities, landscaping, and a connection to the nearby Macaulay Point Park makes the station a positive addition to the local community. Through collaboration with the Pacific Peoples Partnership, Esquimalt Nation and Songhees Nation the public realm design incorporated a carved peace house post, Chief’s chair, First Nations artwork and interpretive signage to help honour the traditional territory of the Lekwungen speaking Peoples.

Rather than increasing the capacity by retrofitting and adding on to the existing station, KWL felt that a full replacement station would be preferred, build to current standards with all new equipment. The challenge with this was the limited space available. With the existing station needing to remain operational throughout the construction and no additional property available on either side, there was a relatively small footprint available. Including more pumps with a longer narrower wet well and pump bay allowed us to fit a new station into the available space.

Optimizing the layout to fit the space available had additional benefits. With multiple pumps to convey peak flows, we were able to reduce capital costs and improve equipment delivery times, installing low voltage drives that are more readily available. We were also able to decrease the size of the electrical service from 2000A to 1600A.

Some components had to be custom designed and modelled before construction. The custom travelling screens are 12m tall, the custom degritter includes an integral high flow bypass, and to fit the small site custom stainless steel turning vanes and baffles were required to guide flow in a U-turn pattern through the station.

Having the new station set back from the existing station created the space we needed to include community amenities reinvigorating the area and providing a welcoming public space.

We have built the largest municipal sewage pump station in BC and changed traditional pump station design. We have optimized the station for 99% of the flows experienced, increasing the efficiency and ease of operations.

Did it all work? During the November 2021 100-yr rainfall event, the station responded well, conveying all flows as expected. The station dataloggers proved that the design and modelling was correct with the station performing flawlessly.