Norrish Creek and Dickson Lake
The Norrish Creek water source currently provides approximately 85% of the system supply. Existing water licenses allow for an annual average withdrawal of 92 MLD with a maximum amount of 141.5 MLD. However these amounts are not achievable with the current infrastructure. Capacity of the pipeline from the treatment plant to the municipalities is restricted to approximately 80-90 MLD. To optimize the amount of water that can flow from the plant, twinning of key pipe segments began in 2009. The twinned length along Maclure Road in Abbotsford was commissioned in June 2010 and construction along Gladwin Road is currently underway.
During typical Norrish Creek conditions, the water treatment plant can treat 120 MLD: 90 MLD by slow sand filtration and 30 MLD via membrane filtration. However, only the membranes can operate through periods of high creek turbidity, which often occur during heavy rainfalls. Since 30 MLD is insufficient output from Norrish to sustain even the system's basic demands, an additional 24 MLD of membrane filtration capacity will be commissioned in 2012 to ensure a minimum of 54 MLD from Norrish at all times.
The existing Norrish water intake has been plagued by debris clogging and winter icing since its commissioning in the 1980s. A new intake is currently under construction and will begin operation mid-2012.
Dickson Lake, located approximately 10 km upstream of the water treatment plant, serves as a storage reservoir to supplement flow to Norrish Creek. The lake was formed thousands of years ago by a landslide. A dam was built in the 1980’s to allow for controlled release of water. Two pipes extend through the dam allowing for gravity release, while a floating pump station allows for discharge from the lake when the level is below the outlet pipes. The lake is generally full from December to June, with varying degrees of drawdown experienced from July through September, and refilling in October and November. Release of water from Dickson Lake is governed by the water licenses, which generally require that flow from the lake slightly exceeds the amount withdrawn from Norrish Creek to ensure sufficient fisheries flows downstream of the intake. Click here for current flow conditions in Norrish Creek.
