Geotechnical Assessment of Alameda Dam

Alameda Dam is a 42 m high and 1250 m long earthdam located in southeastern Saskatchewan. The dam is founded on 30 m of glacial till overlying high plasticity clay shale bedrock. During its construction in the 1990’s, unexpected displacements occurred in the clay shale, which resulted in halting construction for 18 months to facilitate a review of the design. The dam was completed by adding stabilizing berms, and by constructing the remainder of the dam in controlled stages.

In the spring of 2011, the reservoir was surcharged above its full supply level (FSL) of El. 562 m in order to decrease downstream flood flows resulting from high runoff. Concerns regarding the stability of the dam were raised when the displacements in the clay shale increased during reservoir surcharging. An interim stability analysis indicated that the factor of safety of the dam was significantly less than normally acceptable levels.
In response to the concerns, the Water Security Agency expedited a comprehensive stability evaluation of the Alameda Dam, which consisted of additional site investigations, 2D and 3D limit equilibrium analyses, and advanced 2D and 3D deformation modeling (FLAC). This paper describes the assessment methodology, and presents the main results and conclusions of the stability evaluation.

Quinn, J., B. Chin, M. Pernito and J. Scammell. 2014. “Geotechnical Assessment of Alameda Dam,” in GeoRegina 2014:67th Canadian Geotechnical Conference, Regina, Saskatchewan, September 28-October 2, 2014. Canadian Geotechnical Society.

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