Asset Management of Brownfield Reservoirs - Opportunities/Lessons from a Comprehensive Condition Assessment and Remediation Programme

Stephen Molineux (WSP Ltd), Timbi Poon (Beca Pty Ltd)

The failure of several high-profile assets in 2019 triggered Wellington Water to commission asset condition inspections of its client council’s most critical assets to determine the risks and interventions required to prevent critical asset failure. All 137 of the drinking water storage reservoirs operated by Wellington Water were identified as very highly critical. The reservoirs were of varying ages and construction types and included free standing, partially and fully buried reservoirs each presenting its own unique challenges to assessing and prioritizing remedial works.

This paper describes the process of reservoir failure mode identification, catalogued in various themes including being the ability to identify the subtle but very important difference between a reservoir’s component condition grade and its functional performance which is tied back to Wellington Water’s Customer Service goals.

It covers the digitised inspection, assessment, reporting and validation workflow, offering insights as to how other water utility providers around New Zealand may look to adapt a similar data-driven, assessment workflow that can be leveraged to inform rapid decisions through tailored automated outputs.

An output from this work programme included the development of a reservoir visual assessment guideline document – a document that was based off subject matter experts’ interpretations of how the relevant Ministry of Health Guidelines documents for reservoirs should be best applied to the project, all through the lens of the field operative collecting the data.

An interactive digital dashboard tool was also created and is presently being used and remains relevant to both the internal technical teams as well as client-side personnel who have been using it to make rapid, informed judgements on the health of the reservoir network, and ultimately, derive work scopes and budgets from it. It provides examples of how the dashboard has been leveraged to inform answers to questions such as what works would be needed to be undertaken if a reservoir was taken offline, whether or not to undertake seismic strengthening, and should a particular component be replaced or not.

The importance of leakage testing is discussed with regard to informing visual assessment. Lessons learned and applicability of the information obtained is shared to inform decision making not only on the asset tested but also others of a similar construction.

The paper also describes opportunities and challenges of the current tranche of work which involves development of standardized upgrade details/arrangements for existing reservoirs as well as the opportunities to again leverage the dashboards to aid the development of budgets and physical works pricing and procurement models.

Lastly, the paper discusses the lessons learnt on the condition assessment and data capture programme and the risk management systems set up to manage the vulnerabilities uncovered during the assessment programme.