Abstract:
Ontario Power Generation (OPG) owns and operates the Sir Adam Beck Pump Generating Station in Niagara Falls, Ontario. The 300 ha reservoir is retained by a ring dyke which employs an inclined clay core and upstream clay tongue as seepage reduction elements. Since initial filling in 1958, several sinkholes and depressions have developed both within and near the downstream toe of the dyke, raising concern that piping in the bedrock foundation may be active and affecting the dyke integrity. In 2016, as part of long-term remedial measures, approximately 100, 000 m2 of geosynthetic liner and a 1.2 km long grout curtain were installed to reduce the risk of future dyke failure. Drilling and grouting were carried out through the existing dyke via Multiple Pass Sleeve Port pipes (MPSPs). Prior to full-scale production, trial grouting works were carried out downstream of the reservoir to establish means and methods and demonstrate the effectiveness of grouting procedures. Two trial grouting panels were constructed and subsequently exhumed to assess the results of grouting with particular focus on the performance of inflatable barrier bags outfitted onto the outside of the MPSPs in isolating the bedrock contact zone from the overlying overburden and dyke core. This paper summarizes the trial grouting works, findings from panel excavation, and the resulting modifications to the production grouting program along the upstream slope of the reservoir dyke.