The 50 year plan for network infrastructure

This strategy acknowledges that there is an infrastructure renewals backlog, especially in 3 Waters. Renewals funding has significantly increased in the current 10 Year Plan for 3 Waters (an approximate 57% increase from the 2018-28 plan) in order to begin to address this shortfall, however the budget is still constrained due to affordability pressures, market and internal delivery capacities.

The value of theoretical deferred renewals in the 2021/22 year is estimated at approximately $400M. This represents assets still in operation whose theoretical maximum useful lives have been exceeded. At present, renewals are based on the assessed condition and performance of assets. Assets performing well and in good operable condition despite reaching their theoretical maximum useful lives are not automatically replaced.

The DCC has identified work to address the highest priority risks and activities in most need of investment in years 1 to 5 of this 10 Year Plan. However, affordability pressures, market capacity and DCC project delivery capacity and capability mean investment trade-offs have been made. In this plan, renewals funding matches depreciation from 2027 due to affordability and deliverability. Renewals investment will be prioritised in the most need and highest risk areas while market and the DCC delivery capacity is established. The aim is to increase project delivery year on year and if an improved delivery rate is achieved, there is the option to re-allocate funds from later in the plan to earlier years through the Annual Plan process, providing further opportunities to tackle the renewals backlog. Under existing affordability and deliverability constraints, it is anticipated that the DCC would not be able to catch up on the theoretical renewals backlog until 2045.

The aim of the first three years is to increase the delivery market capacity, alongside improving the capability and capacity of internal DCC delivery functions to begin to address the renewals backlog. As detailed design of projects provides more clarity on scope, the estimated costs of renewal projects will become clearer and costs may change. As more clarity on regulatory changes emerges, alongside the capacity issues and cost constraints, the 2024 – 2034 programme will act as a ‘re-set’ for both renewals and new capital. This programme will be based on addressing renewal backlogs as well as meeting enhanced treatment and discharge standards.

Large scale projects are difficult to anticipate in the longer term due to an increasing number of unknowns However, within the timeframe of this 50 Year Plan, most 3 waters buildings and structures will require replacement or significant upgrades to ensure service levels are maintained. Further changes to the 3 waters and transport networks may also be required depending on demographic changes within the city. The impacts of climate change are likely to place pressure on the transport network’s capacity to remain resilient in coastal, flood-prone, low-lying areas and will likely require some mitigation.

3 Waters investment in the short - medium term is to continue pipework renewals and large-scale plant renewals and focus on wet weather capacity upgrades at the WWTPs. These projects are listed in section 7. More clarity on regulatory changes and the outputs of the system plans will be available for the 2024-34 10 Year Plan and so it is expected that the medium to long term capital projects will evolve for the larger treatment plants.

Longer term, the replacement of the Deep Creek and Deep Stream raw water pipelines (including replacing the Taieri River pipe bridge) are planned, with design starting in the medium term. The replacement of these two pipelines is particularly significant as both carry significant risk in terms of the DCC’s ability to supply water. Failure to address these assets in this timeframe would expose the assets to increasing risk of failure denying the city of its two primary water sources.

Significant 3 waters investment is required to service growth within the city, mainly within the networks. Most of the treatment plants have capacity to deal with forecast population changes, however some of the smaller water treatment plants will need upsizing. The solutions to the water treatment plants will be considered as part of the water system plan which may result in rationalising of plants to ensure they are able to comply with any new, more stringent water quality standards introduced through 3 Water’s reform.

Transport renewals in the short – medium term will remain focused on maintaining the road network to appropriate levels of service. Investment decisions will be backed by condition assessments and prioritised according to the function of the road. Improved planning and increased investment will be required for assets such as sea walls, retaining walls and drainage assets in light of changing weather patterns. Larger projects look to address safety issues, improve the networks capacity and to provide transport choice for different modes that will facilitate a decrease in transport carbon emissions and a healthy connected city.

The DCC will continue to invest in relationships with professional and local government bodies such as Water New Zealand, Local Government New Zealand, Society of Local Government Managers, Institute of Public Works Engineers Australasia and Central Government to avoid duplication of effort and identify approaches used by other groups that can be applied in a local context.

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