River Management
Since the main dam, powerhouse and spillway had to be constructed in the river itself, considerable river-management activity was required throughout construction.
River Diversion
River Management was divided into:
- Stage I Diversion involved the Upstream Stage I Cofferdam diverting water over Taskinigup Falls, which allowed the concrete structures to be constructed in a dry environment.
- Stage II Diversion diverted the entire river flow through the completed Spillway by removing a portion of the Stage I Upstream Cofferdam and then constructing the Stage II Cofferdams across the Upstream Powerhouse and across Taskinigup Falls. This allowed construction of the concrete structures to continue as well as construction of the Main Dam in-the-dry.
Forebay Impoundment
Once the concrete structures and main dam were completed, the spillway gates were slowly lowered on October 31, 2011, to reduce the flow rate through the spillway channel, causing water to back up and rise in the immediate forebay area. The three spillway gates were adjusted daily to ensure the increase in water elevation was approximately 0.5 metres per day. After three days of impoundment, spillway gate # 3 was completely lowered to a closed position. The remaining two spillway gates remained slightly open and were adjusted until the forebay water elevation reached its maximum on November 16, 2011.
Rock Plug Removal
The last activity associated with forebay impoundment was the removal of the rock plug at the upstream end of the Wuskwatim Falls channel excavation. Removal of the rock plug was required to improve water flow out of the lake. On July 15th, 2012 the rock plug blast was detonated and mucking of the resulting channel blast rock continued until the end of August.
