Design and construction administration for new treatment plant

Norrish Creek is the principal water source in the region. This project addressed a range of issues including water quality, seasonal turbidity and colour, and the risk of giardiasis.

Norrish Creek is the main drinking water source for the City of Abbotsford and the District of Mission. Water flows through an intake in the creek to the Norrish Creek Water Treatment Plant (WTP). The Norrish WTP filters water through slow sand filters and membrane filters.

Initial flows through the WTP were 60 ML/day via the slow sand filters and 30 ML/day via the membrane filters (90 ML/day total). Treated water from the WTP flows from the clear well and then through the Bell Road valve chamber before being distributed throughout the Abbotsford and Mission water supply systems.

The Bell Road valve chamber contained one motorized butterfly valve which would close and isolate the Norrish WTP when turbidity was high to prevent the clear well from draining. Hence, during high turbidity events, the entire WTP would be offline.

The WTP was upgraded with the addition of membrane filter trains 4 and 5 which increased the membrane filter flow rates to 54 ML/day. Modulating discharge flows is accomplished with the addition and use of one motorized butterfly valve which isolates the main 600mm pipeline through the valve chamber, and two 300mm control valves which operate in parallel.

The flow control is used to reduce flow drawn from the Norrish clear well. In normal operations the slow sand filters are active and the new butterfly valve is fully open. In a high turbidity event the slow sand filters may go offline and the only filtration at Norrish WTP is through the membranes.