Earth Structures & Excavation
Excavation for the principal structures commenced in December 2007 and was completed in February 2009. The work was done in two phases:
Phase 1: in winter 2007 / spring 2008 included the removal of approximately 650,000 cubic metres of overlying soil and bedrock.
Phase 2: had a further 525,000 cubic metres of bedrock removed during the summer and winter of 2008 from the areas of the principal structures and channels.
Total excavations were approximately 1,178,000 cubic metres of overlying soil and bedrock materials. In parallel with excavation, construction of the Stage I Upstream and Downstream Cofferdams were undertaken.
Construction of the main dam, spillway and powerhouse required excavation of approximately 860,000 cubic metres of bedrock and 1 million cubic metres of common excavation. Some of the bedrock excavation was used as rip-rap (large rocks used to prevent erosion of shorelines and dams) but the majority of the materials were disposed of in a permanent earth and rock-filled berm, which was constructed between Taskinigup Falls and Wuskwatim Falls. The General Civil Works Contractor completed the main dam in summer 2011, placing over 145,000 cubic metres of the impervious, granular and rock fill materials.
A channel was excavated immediately north and adjacent to Wuskwatim Falls through the peninsula. The channel improves outflow conditions from Wuskwatim Lake into the immediate forebay (reservoir) area, upstream of the powerhouse.
As with the access road, ceremonies were held to mark significant milestones and the inadvertent unearthing of any sacred sites. Environmental monitoring continued throughout.