1 km long Site C dam reaches major construction milestone

July 2023 construction progress on the Site C dam. (BC Hydro)

A significant milestone in the project to build the Site C hydroelectric dam has just been reached, and it amounts to a major step towards the start of the process of filling up the reservoir beginning in Fall 2023.

BC Hydro announced Monday that the earthfill dam spanning 1 km across the Peace River in the interior had reached completion. It now stands about 60 metres (200 ft) tall — equivalent to the height of a 20-storey tower — and has a width of about 500 metres at its base on the floor of the valley.

A total of 15.5 million cubic metres of material — enough to fill 6,200 Olympic swimming pools or six times the volume of the Great Pyramid of Giza) — were used to build the earthfill dam, with most of the material sourced locally in the Peace Region.

You might also like:

Granular shells, which are larger and heavier, are used on the outside to create a protective, containment shell, while the dam’s core is made of glacial till, which is impervious to water as it contains clay. The material was transported to the dam on a 5 km conveyor belt.

site c dam bc hydro construction progress july 2023

July 2023 construction progress on the Site C dam. (BC Hydro)

Construction on the earthfill dam first began in 2021, after the Peace River was diverted. The next steps are to cap the earthfill dam and build permanent roads for crews to travel across the structure and river.

Site C’s spillways and generation stations are on the south side of the earthfill dam, within a concrete dam built out of 700,000 cubic metres of mass and reinforced concrete.

Before the reservoir can be filled, one of the two tunnels that currently divert the Peace River around the dam site needs to be converted, which is a process of installing large ring-shaped devices inside the tunnels to restrict the flow of water. Tunnel conversion began in July and is expected to reach completion in September.

After the tunnel flow is restricted, the water level in the reservoir will rise. When the reservoir level is high enough for water to flow through the spillway, both tunnels will be closed.

One of the two tunnels that currently divert the Peace River at the Site C dam. (BC Hydro)

site c dam bc hydro construction progress february 2023 10

February 2023 construction progress on the Site C dam. (BC Hydro)

site c dam bc hydro construction progress june 2023

June 2023 construction progress on the Site C dam. (BC Hydro)

It will take about four months to fill the reservoir, which will cover 55 sq km of land — equivalent to two times the land area of the City of Vancouver. The total surface area of the reservoir will be over 93 acres or about 80% the size of the City of Vancouver, stretching a length of 83 km — roughly the same driving distance between the University of British Columbia and Abbotsford. The reservoir’s depth will be up to 52 metres (171 ft).

If all goes as planned, Site C will be operational by 2025, with all six generating units in service. Construction first began in 2015.

It will have an output capacity of 1,100 megawatts and produce about 5,100-gigawatt hours (GWh) annually — enough power for the equivalent of 450,000 homes or 1.7 million battery-electric cars.

July 2023 construction progress on the Site C dam. (BC Hydro)

Diagram of the Site C dam. (BC Hydro)

Shortly after the BC NDP provincial government came to power in 2017, they considered cancelling the Site C project. But ultimately, a decision was made to proceed with the controversial project, as it would still cost $4 billion with nothing to show for it. At the time of the final decision to continue construction, the latest official project increased from $8.8 billion to $10.7 billion. In 2021, the project’s cost further increased to $16 billion, which includes enhanced design considerations to withstand a major one-in-10,000-year seismic event.

Some critics previously suggested the dam would produce an unnecessarily large supply of surplus energy. But as it turns out, BC will need more electricity supply starting at the end of this decade, which takes into account the new capacity that will be gained for BC Hydro’s grid from Site C starting in 2025. This is much earlier than anticipated, with electrical demand increasing by 15% between 2023 and 2030.

Earlier this summer, BC Hydro announced it will make its first call for additional power in 15 years, with the expectation that it will acquire new sources as early as 2028. This call is expected to provide BC Hydro with about 3,000 GWh of additional electricity each year — equivalent to 60% of Site C’s expected output.

The forecasted demand is driven by the electrification of vehicles, homes, businesses, and industry as part of the broader shift to reduce emissions, as well as population and economic growth.

You might also like: