2017 -Tenterfield Creek Dam Upgrade, Post-tensioning or Mass Concrete Buttress? Let the Market Decide

David Guest, George Samios, Richard Rodd

Tenterfield Creek Dam is a 15m high concrete gravity structure that was constructed in 1930 and raised by 1.83m and stabilised using 97 post-tensioned ground anchors in 1974.Recent stability assessments concluded that the dam does not satisfy the ANCOLD Guidelines for Stability of Gravity Dams and that the situation is likely to deteriorate given the questionable performance of the post-tensioning cables and on the grounds of continuing corrosion and demonstrated loss of load.Tenterfield Shire Council is committed to improving the stability of the dam to meet the requirements of the NSW Dam sSafety Committee and engaged Public Works Advisory to assist them achieve this outcome.

Public Works Advisory prepared a dam upgrade options study which selected two options for further consideration. The estimated costs of the two preferred options were found to be potentially close;therefore Tenterfield Shire Council requested that both options be taken to detail design and tender stage to allow the market to indicate which option was in-fact better value.Factors other than construction costs were also considered in the options evaluation process and these factors influenced the selection outcome. The two upgrade options of lowest cost were the conventional gravity dam strengthen solutions i.e. installation of new post-tensioned ground anchors and downstream mass concrete buttressing. The decision to proceed to tender with two options was supported by the other key funding stakeholder, DPI Water.

This paper provides some unique insight on the comparison of conventional upgrade options for concrete gravity dams and also examines some interesting design aspects encounter edduring the design development process

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