GIS based Route and Asset Optimisation for the Western Dams Water Raw Water Supply Infrastructure

Margaret Cobeldick CPEng, Aurecon New Zealand Ltd, Nick Holden CPEng, Aurecon New Zealand Ltd, and Nikhil Susarla CPEng, Watercare Services Ltd

The existing Huia Water Treatment Plant in Auckland is almost at the end of its operational life. A project is currently underway for the planning, design and construction of a replacement plant at a neighbouring site. As part of the new Water Treatment Plant project works, the capacity and resilience of the supply infrastructure from the source dams to the Water Treatment Plant are also being assessed. The existing assets are located through rugged, isolated country of high environmental value, and it is critical that the raw water supply assets will be resilient and able to provide raw water flows to the new Water Treatment Plant for the next 100 years, whilst withstanding potentially worsening adverse weather events that have recently caused severe flooding and land instability issues in the area.

This paper describes the asset selection and optimisation process that is being used to quantitatively select the preferred raw water supply routes. Development of a GIS-based digital tool to follow an adaptive planning type process was required to coordinate and map out the interlinked decisions required on each component of the raw water supply. Some portions of the existing supply pipelines are over 100 years old and require renewal or upgrade for the future Water Treatment Plant. In addition, other key constraints apply to the project including constructability and safety issues, environmental impacts as well as stakeholder expectations. This GIS tool has several key benefits:
 It is allowing Watercare to optimise what components of the existing headworks and raw water system require upgrades or renewals.
 It is allowing Watercare to confirm the timeline and sequence of the asset construction works, which in turn has provided confidence over the forwardcapital works programme.
 The resiliency of the system components and overall system can be assessed and accepted by Watercare.
 The tool provides a graphical presentation of the options assessment which can be used to explain and share the outcomes of the decision process with internal Watercare and external stakeholders in a technical or non-technical manner.
 The tool has ensured that the collective historic data and decisions made on the project are incorporated into the decision-making process and this collective knowledge is not lost.

In development of this tool Watercare now have access to a project level digital adaptive planning tool that can be used to navigate and support decisions where the input data is complex.