Canadian Dam Association Bulletin - Spring 2015 - (Page 10)

GeoteCHniCaL assessment oF tHe aLameDa Dam JoSePh Quinn, P.Geol. AssociAte, enGineerinG GeoloGist, Klohn criPPen BerGer ltd, cAlGAry, AlBertA, cAnAdA bill Chin, P.enG, PrinciPAl, senior GeotechnicAl enGineer, Klohn criPPen BerGer ltd., cAlGAry, AlBertA, cAnAdA mArk Pernito, GeotechnicAl consultAnt, Klohn criPPen BerGer ltd., cAlGAry, AlBertA, cAnAdA JoDy SCAmmell, P.enG, enGineer sPeciAlist, WAter security AGency, Moose JAW, sAsKAtcheWAn, cAnAdA aBstraCt: Alameda Dam, which is owned by the Water Security Agency (WSA), is a 42 m high and 1250 m long earth dam 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 1990s, 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 10 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. rÉsumÉ Le Barrage d'Alameda est un barrage en terre de 42 m de haut et 1250m de long situé au sud-est de la province de la Saskatchewan. La fondation du barrage repose à 30 m dans le till glaciaire sus-jacent un soubassement de schistes argileux d'une plasticité elevée. Pendant sa construction dans les années 1990, des mouvements inattendus se sont produits dans le schiste argileux, forçant l'arrêt des travaux de construction pendant 18 mois pour permettre une révision de sa structure. Le barrage a été complété en y ajoutant des bermes de stabilité, et en construisant le reste du barrage par phases controlées. Pendant le printemps de l'année 2011, le réservoir a été surchargé par rapport à son niveau de retenue (NDR) de 562 m d'elevation, dans le but de réduire les crues en aval émanant des forts ruissellements. Des préoccupations ont été soulevées au sujet de la stabilité du barrage lorsque des mouvements du schiste argileux ont augmenté pendant la surcharge du réservoir. Une analyse intérimaire View past issues of the CDA bulletin online at www.naylornetwork.com/cda-nXt/ http://www.naylornetwork.com/cda-nXt/

Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Spring 2015

Board of Directors
President’s Message
Geotechnical Assessment of the Alameda Dam
CDA 2015 in Mississauga, Ontario
CDA Publications Wrap Up
CDA Directors & Officers – Call for Nominations
Notice of AGM
2015 CDA Awards – Call for Nominations
Buyers’ Guide and Trade List

Canadian Dam Association Bulletin - Spring 2015

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