A sustainable city is engaging in preparation against climate change, focused on building resilient infrastructure and is protective of its residents.
Getting on with the job of protecting the Esplanade and South Dunedin is critical to the financial, physical and mental wellbeing of the residents in St Clair and St Kilda. Many hundreds of thousands have been spent on reports, it is time to take some action...
There are two threats - from the sea and from the sky.
There is a straightforward and affordable plan to safeguard the beach and dunes of St Clair from erosion simply by reinstating groynes in front of Kettle Park.
You can find out much more here: https://stclairbeach.co.nz/
In an unfortunately similar way, various people have known of the urgent need for South Dunedin stormwater protection work.
In 2022 I wrote:
"South Dunedin was hit by a devastating flood in 2015 but only minor improvements have been made to stormwater systems. It is time to improve our protection capability."
Sadly, we were hit with another flood in 2024 with even more water than in 2015. Thanks to those minor improvements and better maintenance, the effect of the deluge was less but while the stormwater system worked better, it was simply insufficient for the needs of South Dunedin.
I had been working on a short term upgrade plan and was able to submit that to the DCC water engineers immediately after the flooding and they improved the proposal which has since been approved by Council for construction early in the 9-Year plan.
There is a 3-stage solution being worked on for the whole catchment plus an interim bandaid for Surrey St wastewater.
Stage 1 - $29.2m - Funded early in the 9-Year Plan, 2025-34
Hillside Rd, Forbury Rd and Bayview Rd stormwater drains can all be improved significantly.
The quickest project is Bayview Rd which requires installation of an additional connection from Bays Junction to the stormwater pumping station on Portobello Rd. In a thorough review of the South Dunedin situation, Opus Engineering suggested that this could make a 13% flood volume reduction catchment wide.
Next is the Forbury Rd aqueduct which cannot handle the volume of water running off the hills beside it in times of heavy rain. This pipe will be replaced with one that will provide 4 times the carrying capacity. No estimate of catchment flood volume reduction has been made for this pipe upgrade, but it will be substantial.
Anyone who has driven along Forbury Rd in times of very heavy rain will know how much water is running across the road and down to Surrey St.
Lastly, the Hillside Rd stormwater drain will get a pumping station near Andersons Bay Rd which will redirect water into the large 9 metre stormwater drain that discharges at Orari St. The aforementioned Opus Engineering report expected that this improvement would make a 10% flood volume reduction catchment wide.
Stage 2 - $104m - Funded throughout the 9-Year Plan
The wastewater treatment plant (WWTP) at Green Island is scheduled and $43 million is funded for a major upgrade which will enable wastewater that comes through the Caversham tunnel to Tahuna WWTP be redirected to Green Island.
Our Infrastructure Strategy includes wastewater network resilience and efficiency, as well as wet weather flow management. In particular, it describes options such pipe upsizing, additional wastewater network storage, locating and addressing areas of high ingress and infiltration, removal of cross-connections, and connection of catchments to Green Island WWTP. This is allocated $61million and includes the catchment of Kaikorai Valley.
Stage 3 - Long Term – Not yet funded
The South Dunedin Future team and our Three Waters Department will shortly be commissioning modelling on the 7 potential futures for South Dunedin, which will provide more clarity on the viability and efficacy of any potential pipe, pump, and nature-based solutions under consideration. That work will help identify the most optimal answers. The residents have clearly identified that they want to stay in South D, they don’t want the status quo and they don’t want managed retreat.
The Residents of South Dunedin also know that large quantities of stormwater accumulate on the surface of parks in the area during a deluge. One of the many options included in South Dunedin scenarios involves joining Bathgate and Tonga Parks to Forbury Park then pumping the water from there.
I include this option here because to me it is straightforward to visualise on the ground, it divides the catchment in two, it requires minimal disruption to existing housing and it presents the greatest appeal to potential co-funders. There are a range of possible layouts though.
Surrey St Bandaid
5-9 Years is far too long to wait for an end to wastewater emerging from inspection covers onto Surrey St. I had been discussing this situation with staff since October last year, but it became imperative in July when it happened during a relatively small downpour. I asked the engineers to look urgently for a rapid repair that might fill the gap until the proper job could be completed.
Two promising fixes have been found after examining several, but they still need investigation, testing and planning. More information will appear when appropriate.