This section covers the current condition and situation of the city’s 3 waters and transport infrastructure. The DCC’s assumptions on asset lives are attached as Appendix A.
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3 Waters
As one of the country’s earliest metropolitan centres, Dunedin’s 3 waters infrastructure pre-dates that of other centres. Some assets are older than 150 years and still operate as essential pieces of the network today. As Dunedin has grown, so have the 3 waters networks, resulting in widely distributed networks with a broad range of pipe materials, diameters and construction methods. As areas were connected to the different networks at different times, there can be wide variation in age, condition and capacity of assets in the same location. As a result of age, many assets need repair and/or replacement. We mainly deliver our operational services in house, but some specialist resources are outsourced such as specialist maintenance providers, consultant services, design services and capital delivery contractors across 3 waters. This strategy does not look to change the service delivery approach as there is little benefit while the 3 Waters reform programme is unfolding.
Water supply
Today, most of the water supply needed for the city comes from the Deep Stream and Deep Creek catchments. This is then treated at Dunedin’s two major treatment plants - Mount Grand and Southern - before being distributed for public consumption. In addition, the DCC operates four smaller community water treatment plants: Waikouaiti, Outram, West Taieri and Port Chalmers. The Port Chalmers water treatment plant is only operated during periods of high demand, such as cruise ship season, to supplement the main metropolitan supply.
Wastewater
Dunedin’s Main Interceptor Sewer was constructed between 1903 and 1908. This sewer, which has gradually increased in size, is still in use today, running from the Dunedin Railway Station to the Tahuna wastewater treatment plant. It takes wastewater from a large part of the Dunedin metropolitan area, the West Harbour catchment as far as Port Chalmers and the East Harbour as far as Portobello. The second largest wastewater system collates flows from the north-west and west of the city, Brighton and Waldronville and is treated at Green Island wastewater treatment plant. In addition, the DCC operates wastewater networks and treatment plants at Mosgiel, Middlemarch, Warrington, Seacliff and Waikouaiti/Karitane.
As time has progressed, and community expectations around wastewater discharges have changed, treatment plants have been consolidated and upgraded. The most recent major upgrade, completed in 2016, was to the Tahuna wastewater treatment plant, with minor upgrades underway at Seacliff wastewater treatment plant.
Stormwater
Stormwater infrastructure in Dunedin consists of public and privately owned open and piped watercourses, the DCC owned reticulated stormwater networks and Otago Regional Council owned or managed drainage schemes, streams and river systems. As Dunedin has grown, the stormwater network has grown with it.
Increases in the scale and frequency of rainfall events and growing public expectations about the quality of stormwater discharges to the environment are significant challenges to be met by all those who own or manage stormwater infrastructure.
Due to the complex nature of stormwater systems, addressing stormwater issues can be expensive, require specialist skills and a catchment-based approach with the coordination of many individual watercourse owners. The current requirement for private infrastructure owners to maintain their watercourses does not always result in the best overall outcomes for the city and may be better managed by one entity. However, the DCC’s drainage rates do not currently make any allowance for maintaining infrastructure identified as privately owned.
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Transport
Dunedin’s transport network is relatively complex in comparison to most provincial centres. It is made up of a diverse range of assets and has an equally high mix of urban and rural roads within a varied topography. Footpaths are generally in poorer condition than the roads. Maintaining transport levels of service is supported by the funding arrangements with Waka Kotahi year on year.
Resilience in the road network is an ongoing issue as many roads across the city are at risk from flooding, erosion and king tides. Heavy vehicle movements continue to put pressure on road pavements and deterioration of roading assets is being observed. This is particularly evident on roads from the south to the Port and the inner harbour. Certain routes across Dunedin are seeing congestion in short commuter peak travel windows.
In addition, the city suffers from the social cost of road trauma with reasonably high crash statistics across the city. Crash statistics are particularly high between motor vehicles and vulnerable road users such as pedestrians. Gaps exist in the strategic cycling network with approximately 50% of the network currently implemented across the city.
Maintenance services are outsourced via a 10 year maintenance agreement with Fulton Hogan. Other capital works and structure inspections are also outsourced to contractors