Stormwater Asset Renewals

Stormwater is often looked at as the ‘poorer cousin’ in the 3 Waters family and historically has not had the focus or investment it has deserved. In recent times, effects from urban intensification and climate change have become more noticeable through frequent and larger flooding events and the decline in quality of our waterways. This is further exacerbated by the fact that a large proportion of stormwater assets within Tauranga are near the end of their design life and are at risk of failing, as well as falling significantly behind current performance standards. As a result, Tauranga City Council (TCC) are ramping up it’s investment in the renewal of stormwater assets.

Vitruvius have been assisting TCC in the investigation, assessment, and prioritisation to renew existing stormwater assets, based on condition assessments and network criticality. TCC have identified a number of existing assets that are at risk of failure through a city-wide CCTV investigation programme. Vitruvius were involved in the initial screening of these assets and provided a more in-depth assessment for each asset to answer questions such as “Is the condition really as poor as first thought?”, “When is this asset likely to fail?” and “What are the consequences of it failing?”.  As well as the pipe condition, the performance of the pipe was also assessed to answer further questions such as “How under capacity is this pipe?” and “What does the size of the pipe need to be to meet future climate and development demands?”.  Options were then considered to “do nothing”, repair or upgrade – with the design, constructability and general project risks being taken into account.

With this key information we were able to grade the condition and performance for each asset, assign a risk rating as well as cost to undertake the works. This enabled each asset to be compared objectively and allow TCC to determine what assets need to be prioritised, and where the opportunities are to integrate with wider TCC future or planned upgrades.

This work is to form the basis of a future renewals programme that ensures a targeted and planned upgrade of stormwater assets, medium to long term budget certainty, a pipeline of work for Contractors, and a smoother transition into the new Water Entity B.