A Model to Estimate the Cost of Stormwater Improvements for the Auckland Region

Auckland Council is responsible for the management of the estimated $2.5 billon dollars worth of stormwater infrastructure which services over 510,000 rateable properties within 235 catchment management areas. In order to meet strategic stormwater management objectives, define funding level gaps and reach stated levels of service, it is necessary to look forward into the future and estimate the amount of capital expenditure required to improve system function and performance.

This paper describes the development and outputs of a Stormwater Cost Estimation Model (SWCEM) designed to be a tool to estimate the “day one” cost needed to deliver improvement projects and programmes across the range of Auckland Council’s stormwater activities in order to meet Council’s objectives and Levels of Service. In particular the foundation datasets, levels of service assumptions and equations which make up the model will be discussed.

Development of the SWCEM has involved staff across multiple disciplines including GIS, Planning, Asset Management and Modelling. The consolidation of the Stormwater Unit from the legacy councils has provided an opportunity to draw together the best available data from across the region.

This exercise identified a range of costs to inform potential budget envelopes as well as a range of lessons learned and recommendations.