Shoring up the foundation of the right bank of the Site C dam, midway through the project, cost an extra $1.1 billion.
Remedying two tension cracks in the left bank — cracks BC Hydro had previously deemed “low-probability, high-consequence” — delayed the project for a year.
These are two of the “lessons learned” detailed in a new report from B.C. Hydro that seeks to explain the spiralling cost of the dam’s construction.
This report is in response to a May 6 directive from the B.C. Utilities Commission for BC Hydro to break down what led to the project costing nearly twice its initial budget, and how lessons can be applied to future major projects.
The report finds several main issue areas: The project was more complex and challenging than anticipated, the COVID-19 pandemic led to delays, and several low-probability geotechnical problems cropped up.
Local environmental factors also contributed to costs, including 60-degree Celsius temperature swings between winter and summer, wildlife issues such as bear denning, and the need to attract a large workforce to a remote area.
From the project’s initiation in 2014 to completion in 2024, the budget was increased twice, from $8.775 billion to $10.7 billion in 2018, and then again to $16 billion in 2021.
Filling of the reservoir was completed in August 2024, and by the same month in 2025, all six electrical generating units were online. Site C now produces approximately 1,230 megawatts at peak output, or roughly enough electricity to power 500,000 homes.
Some of the issues detailed in the report could have been anticipated.
“While the COVID-19 pandemic was unforeseen, the potential for geotechnical challenges on the left bank and right bank was understood,” the report’s executive summary says.
The left and right banks were extensively investigated for nearly 40 years before the project got underway. The report finds the budget and schedule impacts of these types of risks must be communicated.
“[G]oing forward, BC Hydro should consider how to better communicate the breadth of low-probability, high-consequence risks on a project that have the potential to result in significant budget and schedule impacts, if they materialize,” the report says.