Cofferdams
A cofferdam is a small temporary dam consisting of rockfill and granular borrow material.
The role of the cofferdam is to dewater the future dam site by redirecting the river water into the diversion
tunnel. Impervious materials such as till, available in large quantities in the James Bay region, ensure watertightness.
Dam
The rockfill dam will be 67 m high with a crest length of 860 m. It will be used to create
a water reserve and increase the head. The till core and transition layers, built up in alternation, will make
the structure impervious.
| Structure |
Type |
Height
(m) |
Crest
length
(m) |
Crest
width
(m) |
Volume
(m3) |
Crest el.
(m MSL)
|
| Initial cofferdam |
Rockfill |
12.5 |
240 |
12 |
70,000 |
235.6 |
| Upstream cofferdam |
Rockfill |
24.5 |
263 |
10 |
215,000 |
248.2 |
| Downstream cofferdam |
Rockfill |
10.2 |
201 |
14 |
33,000 |
231.4 |
| Dam |
Rockfill |
67 |
860 |
10 |
2,500,000 |
286.5 |
|
