Isolation of a Critical Asset in the Water Supply Network - Fraser Coast Regional Council

Abstract

How do you take your largest water reservoir in network offline for a period of three months for re-lining? The short answer is, you bypass it. The reality (or the long answer) is that is takes 12 months of planning and trials to ensure water security. The Urraween Reservoir at 32ML, is the largest potable water storage in the Hervey Bay water supply network and is the main buffer storage for the majority of Hervey Bay suburbs. The reservoir is also the lowest in the network and has a pump station to boost the flow to the final gravity supply reservoirs before the reticulation network. The configuration of the reservoir site pipework has all flow entering the reservoir before being able to be pumped. Isolation of the reservoir would eliminate the existing pump station and limit flow to gravity, which was deemed to provide insufficient security of supply. The reservoir is an earth based dam style reservoir with a HDPE floor liner and geomembrane floating cover. The floating cover on the reservoir had reached the end of its useful life (approx. 22 yrs) and required replacement. To achieve this the reservoir had to be removed from service for a period of 3 months while the liner and cover material were removed and replaced. The complexity was that, since it was 22 years since the last time this asset had been taken offline, there was no documented process to ensure water supply security. This presentation covers the process that Fraser Coast Regional Council went through to ensure the security of supply during the period the reservoir was offline.