Dam Busters! - The Decommissioning of the Historic Reservoir Creek Dam
Annual Conference
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The Reservoir Creek Dam in the Tasman district is the site of a historic dam which was inaccessible to the public, at risk of structural failure and a barrier to fish passage.
The dam was originally built in 1890 as a water supply reservoir. However, it has not supplied water since the mid-seventies and from late 2000 there have been concerns about its stability and the risk of failure. In December 2011, a severe rain event in the region caused two slips at the dam blocking the spillway.
The Tasman District Council decided to decommission the dam and engaged MWH NZ Ltd (MWH) in the planning, design and construction monitoring for the scheme. Throughout the planning phase, a wide range of options were considered from pipe thrusting to complete removal of the dam.
The final design was a new concrete spillway through the existing dam. To reduce the hydrostatic pressure on the dam, the new inlet invert was set 3 m lower than the existing.
The decommissioning provided the opportunity to reshape the dam, and it is now an integrated community asset, that is safe, has improved ecological features whilst also retaining its historical value.
This paper will discuss the challenges, solutions and outcomes of this unique project.