ABSTRACT:
Development of the Revelstoke and Mica hydroelectric projects on the Columbia River in British Columbia resulted in raising water levels along the toes of nearly 1000 km of steep mountain slopes. Dozens of large, potential or existing, rock slides have been identified and investigated to varying degrees. Investigations at Checkerboard Creek Rock Slope (~3Mm3), located just upstream of Revelstoke Dam, were concluded in 2005 with the testing of various slide scenarios in a scaled physical hydraulic model. Long-term monitoring at Checkerboard Creek Rock Slope was essential for the stability assessment and will continue indefinitely so as to provide a check on assumptions made and provide warning of any change in behaviour. The second case history, Little Chief Slide (~ 900Mm3), located just upstream of Mica Dam, was first investigated in 1968/69 prior to reservoir filling. After over 30 years of monitoring slope performance, additional investigations were carried out in 2004/05 when BC Hydro recognized that there was insufficient understanding of the slide to confidently predict its future behaviour, especially during an earthquake. These investigations illustrate the need for deep, subsurface drilling, installation of automated instrumentation, and long-term monitoring to develop reliable geological and geo-hydrological interpretations.
1 INTRODUCTION
Development of the Revelstoke and Mica hydroelectric projects on the Columbia River in British Columbia (Fig. 1) resulted in raising water levels along the toes of nearly 1000 km of mountain slopes. The stability of these slopes has been a design or reservoir operation requirement since before 1961 (Mylrea 1978). The most intensively investigated slopes are Checkerboard Creek (Watson et al. 2006), Downie Slide (Imrie et al. 1992), Dutchman’s Ridge (Moore 1999) and Little Chief Slide. Both Downie Slide and Dutchman’s Ridge have been stabilized using drainage tunnels and drain holes.
