Robert-Bourassa Dam: The Crown Jewel of Quebec's James Bay Project

**Robert-Bourassa Dam** (formerly LG-2) on the La Grande River in northern Quebec is the crown jewel of the **James Bay Project**, one of the largest hydroelectric developments in history. Its **5,616 MW** underground powerhouse — the **largest in the world** — is housed in a cavern excavated from the solid granite of the Canadian Shield, 137 meters below the surface. Completed in **1981**, the dam generates roughly 15 percent of all electricity consumed in Quebec.

Introduction

The James Bay Project, developed by Hydro-Québec between 1971 and 1996, diverted and dammed multiple rivers flowing into James Bay, creating a system of reservoirs spanning over 11,300 square kilometers of subarctic wilderness. The project was a source of immense pride for Quebec, solidifying the province's identity as a leader in clean energy, but it was also deeply controversial among the Cree and Inuit peoples whose ancestral territories were flooded.

Engineering & Structure

• Type: Earth-fill dam with rock-fill
• Height: 162 meters
• Crest Length: 2,835 meters
• Underground Powerhouse: World's largest (483 m long, 27 m wide, 47 m high)

Robert-Bourassa Dam is an earth-fill structure rising 162 meters above the La Grande River, with a crest length of 2,835 meters. Multiple dike systems extend the containment across the flat terrain, creating a reservoir of approximately 2,835 square kilometers. The dam is relatively simple in design, but its underground powerhouse is an engineering marvel.

The powerhouse cavern measures 483 meters long, 27 meters wide, and 47 meters high — large enough to fit two football fields end to end and a 15-story building. Sixteen 351 MW Francis turbines are arranged in a row within this granite chamber, connected to the reservoir by 16 penstocks descending from the surface. The excavation removed 1.2 million cubic meters of rock.

Geographic Setting

• River: La Grande River
• Location: James Bay region, Nord-du-Québec, Canada
• Coordinates: 53.78°N, 77.45°W
• Reservoir Area: 2,835 km²

The La Grande River flows 893 kilometers westward across the Canadian Shield to James Bay. The dam is located in the subarctic boreal zone, approximately 1,500 kilometers north of Montreal, where the landscape is an endless expanse of black spruce, muskeg bogs, and rocky outcrops. Winter temperatures regularly drop below minus 40°C, and the brief summer brings clouds of black flies and mosquitoes.

The James Bay Project dramatically altered the hydrology of the region by diverting the Eastmain, Opinaca, and Caniapiscau rivers into the La Grande River basin, roughly doubling its natural flow. This created a vast system of interconnected reservoirs across the subarctic landscape. The Canadian Shield bedrock — Precambrian granite over 2.5 billion years old — provided a stable and impermeable foundation for the dam and reservoir system.

Hydroelectric Power

• Installed Capacity: 5,616 MW
• Annual Output: ~35 TWh
• Turbines: 16 × 351 MW Francis turbines
• System Total: James Bay system: ~16,000 MW combined

Robert-Bourassa's 16 turbines generate approximately 35 terawatt-hours per year, making it one of the most productive single hydroelectric facilities in the world. The dam is the largest of eight generating stations in the La Grande Complex, which has a combined capacity of approximately 16,000 MW — making it the second-largest hydroelectric system in the world after China's Three Gorges.

The electricity is transmitted to southern Quebec and exported to the northeastern United States via 735 kV transmission lines spanning up to 1,500 kilometers. Hydro-Québec's exports to New York, Vermont, and New England are significant, and contracts for James Bay power are periodically the subject of cross-border negotiations between Quebec and US states seeking clean energy.

Environmental & Social Impact

• Area Flooded: 11,335 km² (total James Bay project)
• Cree Opposition: James Bay Cree fought the project in court
• Mercury Contamination: Flooded vegetation released mercury into food chain

The James Bay Project flooded approximately 11,335 square kilometers of subarctic wilderness, affecting the traditional hunting, fishing, and trapping territories of the James Bay Cree and Inuit. The Cree, led by Grand Chief Billy Diamond, fought the project in court and negotiated the James Bay and Northern Quebec Agreement of 1975 — one of the first modern land-claims agreements in Canadian history, providing financial compensation and self-governance provisions.

The flooding of boreal forest released mercury from soil and vegetation into the aquatic food chain, contaminating fish — a dietary staple for Cree communities. Mercury levels in some fish species exceeded safe consumption guidelines for years after flooding. The social disruption of the project — altered river flows, loss of hunting grounds, influx of construction workers — had profound and lasting impacts on Cree communities that are still being addressed.

Key Facts

• Robert-Bourassa houses the world's largest underground powerhouse (483 m long).
• Its 5,616 MW capacity generates approximately 35 TWh per year.
• The James Bay Project flooded 11,335 km² of subarctic wilderness.
• The James Bay and Northern Quebec Agreement (1975) was a landmark indigenous land-claims settlement.
• Mercury contamination of fish affected Cree communities for years after flooding.

Fun Facts

• The underground powerhouse cavern is so large that construction workers drove trucks through it during excavation.
• During construction, the workforce lived in purpose-built camps accessible only by air for much of the year — the permanent road to the dam site was not completed until after the project was nearly finished.
• The La Grande River's natural flow was roughly doubled by diverting three other rivers into its basin — fundamentally rewriting the hydrology of northern Quebec.

Final Thoughts

Robert-Bourassa Dam and the James Bay Project represent one of the most ambitious hydroelectric developments in history, transforming Quebec's economy and energy identity. The project's scale is matched by the complexity of its social legacy — a landmark in both engineering achievement and indigenous rights negotiation.