GSS Civil Works

The Generating Station and Spillways (GSS) Civil Works is one of the largest contracts awarded for the Site C project, which is a dam and generating station in northeastern British Columbia (BC). The GSS Civil Works is the portion of the Site C project that AFDE Partnership is responsible for constructing.

The contract includes construction of the generating station (or powerhouse) and penstocks, spillways and power intakes, and minor concrete work around the site.

The GSS Civil Works is a big job. AFDE Partnership will place approximately 700,000 cubic metres of mass and reinforced concrete for the spillways, powerhouse, and penstock encasement—that’s equal to 280 Olympic-size swimming pools of concrete. AFDE is also responsible for processing and production of all aggregates and granular materials required for the works.

The project will use 34,000 tonnes of rebar, equal to 4.5 Eiffel towers. Once complete, the formed surfaces of the GSS will be enough to cover 63 National Football League football fields.

More details about works scope components can be found below.

Credit: BC Hydro


The powerhouse will be the heart of the Site C dam. It is the facility that receives the water from the reservoir via the penstocks and runs it through the turbines, using it to create energy for the electric system, before releasing that water back into the river.

AFDE’s scope of work inside the powerhouse includes:

  • Construction of the powerhouse structure, with six power-generating units
  • Procurement, fabrication and erection of structural steel
  • Procurement and installation of embedded pipes, ground grid and conduit
  • Concrete placement to secure the turbine-generators
  • Installation of hydromechanical equipment

Intakes and Penstocks

AFDE’s scope of work for the intakes includes:

  • Procurement and installation of intake trash racks (steel grids that ensure debris and material do not enter the penstocks and turbines) and anti-vortex devices
  • Installation of the intake maintenance and operational gates and embedded parts
  • Construction of the intake concrete structures and transition block (between the spillway and intakes)

AFDE is also responsible for the procurement, fabrication, and erection of six penstocks. Penstocks are large water conveyance pipes made of steel encased in concrete. Each penstock measures 10 metres in diameter and 80 metres in length, nearly as wide as a three-lane highway.  After they are installed, the penstocks are encased in concrete.


Spillways are a prime safety feature of the dam and are typically only used during freshet and flood events. AFDE will construct 395,000 m3 of cast-in-place concrete for the spillway.

Looking from the bottom of the spillways to the top of the headworks will be the same as staring up at a 28‑story building. Each spillway bay will be equivalent to a 17-story water slide that is five highway-lanes wide.

Site C Project

The Site C project consists of a dam and generating station on the Peace River in northeast BC. It will be the third dam to be built on the Peace River, owned and operated by BC Hydro.

Once completed, the project will provide 1,100 megawatts of capacity and about 5,100 gigawatt hours of energy each year to BC’s integrated electricity system – enough energy to power the equivalent of about 450,000 homes per year in BC.

The image below showcases the various components of the Site C project.

Credit: BC Hydro

Curious about what the Site C project entails and how GSS Civil Works fits into the overall project? Watch the latest Site C construction sequence video.