2019 – The Lessons Learned and Construction Challenges for the Leslie Harrison Dam Upgrade

Ryan Cantrill, Peyman Andaroodi, Colin Thompson

Leslie Harrison Dam is located on Tingalpa Creek in the Redlands region, approximately 18 km southeast of Brisbane. It is classified as an extreme hazard category dam with a large population at risk only a short distance downstream.

The dam comprises a 25 m high zoned earthfill embankment, with a dry well concrete intake tower and an outlet conduit located at the base of the dam near the old river channel. The spillway has a 43 m wide concrete gravity ogee crest, with a concrete lined chute terminating in an energy dissipator structure.

Seqwater is undertaking a staged upgrade of Leslie Harrison Dam to address deficiencies identified during the Portfolio Risk Assessment (URS 2013) and Geotechnical Investigations (GHD 2016).
While the dam has met the water supply needs of the community for the past 50 years, the upgrade ensures local residents will be well served into the future. Additionally, the structure will meet the most up to date requirements of dam safety management and national industry standards.

Construction of the Stage 1 upgrade commenced in June 2018 and involved the removal and replacement of liquefiable material in the foundation, modernisation and extension of the outlet works, addition of a new downstream filter buttress to the embankment, and lastly, the installation of both active and passive anchors within the spillway ogee and lower chute floor.
As with any major project, the works involved a number of challenges that had to be addressed. This paper provides an insight into the key challenges encountered and how these were overcome by the design and construction teams using practical engineered solutions. The intent is to provide the reader with an account of the “lessons learned” during the construction phase, along with recommendations for future dam upgrades.

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