Water Matters: The South Fork Dam

Apr 07, 2015

In the first post of this series we explored Jump Lake - the start of the journey for Nanaimo's water. In this segment, we move downstream with the water, as it is released from Jump Lake and flows to the South Fork Dam. This is where the water enters twin pipelines for its journey to the City.


A wintery aerial view.


The man-made waterfall upon its completion in 1931.


The man-made waterfall now.

Contracted to Jamieson Construction Co Ltd of Vancouver, the dam was built over 1930 and 1931. 


Downstream face of arch during construction.

Incredible foresight was used when planning and designing the dam as they built it at an elevation to allow water to flow to Nanaimo by gravity instead of using pumps (although there are a few areas in Nanaimo that require pumping due to their elevation). The dam is formed in an arch configuration and leans downstream 32 feet. The City has saved (and continues to save) hundreds of thousands of dollars in electricity costs from having the dam built this way. 


Downstream face of completed arch.

Completion of the dam was nearly a year behind schedule due to many setbacks such as the project being flooded out many times and a fire. The dam is 165 feet wide and 100 feet tall and is built of unreinforced concrete.


Completed structure.

During construction, concrete was poured 24 hours a day from August 13, 1931 through to October 12, 1931 - 18,447 bags of cement were used. 


This plume of water is the low level outlet, which ensures sufficient water flow for cutthroat trout in the river.

The dam holds 2 million cubic metres of water and the reservoir is kept full. This creates the hydraulic grade line that allows Nanaimo's water system to be fed by gravity. For the past 15 years or so, power has been generated at the dam for local needs.


South Forks reservoir.

Once water leaves the dam it travels through two pipelines to the City; one 30 inches (750 mm) in diameter and the other 48 inches (1200 mm) in diameter. 


A look downstream.

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