2022 – Innovative solution allowing the use of challenging earthfill materials

Daniel Jirik – Civil Engineer, Entura, Alan White – Specialist Engineer Dam Infrastructure, TasWater, Angus Swindon – Director & Principal Consultant, Tasset Consulting

Henderson Dam on Flinders Island was constructed in the 1970’s and raised in the 1980’s. It is the primary storage facility for Whitemark and required augmentation to ensure a reliable water supply over the long term. A comprehensive surveillance review highlighted significant flaws in the dam. The key risks requiring mitigation were seepage along the spillway/embankment interface and insufficient spillway capacity. Risk mitigation and capacity augmentation measures resulted in a complete rebuild of the existing dam in 20212022. This paper examines aspects of construction compaction control measures related to use of sandy, very low plasticity soils under wet weather conditions. Horizontal drains were considered to manage pore pressure and their effectiveness was determined through visual inspection and use of a shear vane.

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