Japan Gulch Ultraviolet Disinfection Facility

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The Capital Regional District provides potable water to a population of 310,000 in Victoria and the surrounding area. The District’s water supply comes from pristine lake sources, high above the City. The lakes are in protected watersheds and the raw water quality is generally very high.

Due to concerns over pathogens, such as Cryptosporidium and Giardia, the District elected to provide UV primary disinfection at its water treatment sites. In July 2002, Associated Engineering was retained to carry out the detailed design and construction services for the UV facilities.

The treatment facility at Japan Gulch treats approximately 90% of the District’s water needs. The facility includes 15,600 mm diameter, medium pressure UV reactors. At a capacity of 580 ML/d, the installation was the largest UV installation in Canada at the time. The reactors are arranged in parallel with the last unit configured so that it can be used for on-site equipment validation. The facility includes extensive sampling equipment including online UV transmittance monitoring.

The facility layout is based on a two-storey structure, with the major pipe headers in the lower floor. A major valve chamber includes ten large diameter butterfly valves complete with bypasses. The compact layout of the facility minimized the 1,200 mm and 1,500 mm diameter piping costs associated with the project. The facility is particularly unusual as the system runs at a relatively high pressure of 700 kPa. The system also has a flow demand control algorithm which we developed specifically for this project.

The site posed many design challenges including steep terrain, limited access and a number of physical constraints including a nearby rail line and other existing infrastructure. The project is valued at $11.5 million and was commissioned in April 2004.