Wellington Dam upgrade
Client: Water Corporation
Location: Bunbury, Western Australia
Date: April 2009 – October 2011
Delivering innovative and cost-effective design to upgrade a dam to meet modern safety standards and reduce flood risk.
Background
In the early 2000s studies found that the 34m-high concrete gravity Wellington Dam (Bunbury, WA) needed to be strengthened to meet ANCOLD flood guidelines and pass the Probable Maximum Flood (PMF), for the safety of the more than 1000 people at risk downstream. The works were undertaken through an Alliance delivery strategy to foster innovation in the design and construction to meet the client’s requirements of a safe and cost-effective solution.
Solution
Entura was the lead designer of the remedial works on this project. A number of strengthening options were investigated and costed before adopting a solution of large 91-strand ground anchors, housed in bridge piers across the spillway with a permanent low-level bridge. This design had significant advantages in that the bridge was at the same level as the abutment sections (reducing its length), the deck was designed to wash away in extreme floods reducing the hydraulic loads on the dam, the bridge provided both construction and permanent access to the anchor heads for inspection and testing; and housing the anchor heads in the piers made them easy to inspect and kept them out of the water for all but extreme floods. Ancillary works to improve access and safety of the outlet works, dam gallery and instrumentation were undertaken to bring the dam up to contemporary standards.
Outcome
By working closely with Water Corporation and the construction team in an Alliance format we were able to develop an anchoring solution to stabilise the dam which was safe to construct, safe to operate and could meet the challenging budget expectations of the client. The Alliance was an outstanding success with the overall project completed 4 months ahead of schedule, 15% under budget and with no lost time injuries on a project with significant safety hazards, including working at heights and over water. Despite working within the boundaries of a National Park and close to Aboriginal heritage, there were no significant environmental issues.
