Pio Shores Stormwater: Frequently Asked Questions

Over the last few years, we have carried out a number of investigations to better understand how stormwater behaves in Bowentown, Pio Shores and the Seaforth Road corridor. Like the rest of Waihī Beach, Bowentown has natural geography that makes draining stormwater challenging. The land is low‑lying, very flat and close to the coast, and much of the drainage relies on dune soakage rather than deep underground pipes.

Like the nearby coastal area Pāpāmoa, roads in Bowentown and Pio Shore are designed to carry stormwater during heavy rain. They are intended to act as natural channels - helping to direct and temporarily hold water while it drains away and the pump systems have a chance to work.

There are also practical and environmental limits to how stormwater can be managed in this area. The dune basin is designed to fill during heavy rainfall, and water may temporarily pond near the walkway until it naturally soaks away. Council cannot discharge water through the dunes to keep the walkway clear, as this would damage the dunes and breach consent conditions.

Other options have been considered. Larger pipes have been installed in parts of Pio Shores, but modelling shows that while they can help reduce how long flooding lasts, they do not lower peak flood levels during major storm events. Alternatives such as detention tanks or pumping water further away are also not practical — detention tanks would need to be extremely large to make a meaningful difference, and pumping further north would require long pipelines and significant cost.

Because of its natural conditions, this area will always experience flooding during heavy rain. The challenge is how to lessen the effects as much as we can, and to make sure water can drain away more effectively after storms. The work below reflects the steps we have taken to understand the issues and improve the system.

1. Stormwater investigations and recommendations

Pio Shores Stormwater Basin Assessment (2021)

This assessment looked at how stormwater flows through Pio Shores, how quickly water soaks into the dunes and where flooding is most likely to occur.

The report found that:

• The land is very flat, so water drains slowly.
• The dunes can absorb water, but only at a limited rate.
• During big storms, more water arrives than the dunes can soak up at once.
• Some parts of the network did not have enough capacity to move water away quickly.

How we used this information:

• We designed upgrades to the pump stations and pipe network.
• We improved the dune soakage basins so they can temporarily hold more water during storms and allow it to soak away naturally.
• We carry out post‑event inspections to check dune stability and vegetation health.
• We identified where further capacity improvements were needed. This information informed both completed and current stormwater improvement projects in the area.

Source:

Pio Shores stormwater upgrade – Resource Consent Assessment (2022)

This report supported the resource consent for the upgraded stormwater system. It assessed how the new pump stations and soakage basins would work and how they might affect the dunes and surrounding environment.

The report found that:

• Pumping stormwater into the dunes works well, but the dunes must be protected from oversaturation.
• The upgraded pump stations would reduce how long water stays on the surface.
• Very large storms will still cause flooding, but for shorter periods.
• Environmental effects can be managed with monitoring and careful operation.

How we used this information:

• We upgraded the Papaunahi and Tui Park pump stations.
• We put monitoring processes in place to check dune stability after major rain events.
• We refined how stormwater is directed into the dune basins to reduce erosion risk.

2. Stormwater Infrastructure Upgrades

Pump Station Improvements

We upgraded the Papaunahi and Tui Park stormwater pump stations to improve reliability and reduce the duration of ponding during heavy rain. These upgrades were designed to work with the natural dune system while protecting dune stability.

Pipe Network Enhancements

We installed larger stormwater pipes in parts of Pio Shores and along Seaforth Road. These upgrades help move water more efficiently and reduce the time it takes for surface flooding to drain away.

Dune Soakage Basin Improvements

We improved the dune soakage basins so they can temporarily hold more water during storms and allow it to soak away naturally. We also carry out post‑event inspections to check dune stability and vegetation health.

No - the pumps continued to operate through-out the storm.

We received some enquiries from residents who thought the pumps may have stopped because they couldn’t hear them running. However, the pumps are relatively quiet when operating, especially during a storm when there is significant background noise from wind and rain.

We actively monitor the pump stations remotely, which allows us to track their performance in real-time. During this event, the pumps continued to operate as expected and played an important role in helping to drain floodwaters.

In areas like Pio Shores, the system is designed to work together - with roads acting as natural channels to help direct and temporarily hold water while it drains naturally, as well as giving the pumps more time to work.

The pumps are specifically designed to reduce how long floodwater remains on roads and surrounding areas, rather than to prevent flooding entirely. During large storms with heavy rainfall, the volume of water can exceed what the system can remove immediately, meaning some flooding is expected until levels begin to recede.

This design approach is based on earlier investigations, including the Pio Shores Stormwater Basin Assessment (2021), which found that the dunes can only absorb water at a limited rate.

During the January 2026 storm, the Papaunahi pump station tripped and stopped operating. This was likely caused by water affecting electrical components. A manual reset was required, which operators completed once on site.

Even when pumps are operating normally, flooding is still expected during large storms. The pumps are designed to reduce how long water stays on the surface, not to prevent all flooding.

This design approach is based on earlier investigations, including the Pio Shores Stormwater Basin Assessment (2021), which found that the dunes can only absorb water at a limited rate.

No. There is no set limit on pump operating hours. The main constraint is protecting the coastal dune system, which can become unstable if too much water is pumped into it for too long.

This was highlighted in the Pio Shores Stormwater Upgrade – Resource Consent Assessment (2022), which confirmed that dune stability must be protected when designing and operating the stormwater system.

Council carried out pre-storm checks and cleared the grill before the rain. Crews also inspected it during the event. However, debris can build up quickly during heavy rain, and crews cannot be stationed at every outlet continuously.

Yes. After major rain events, Council inspects the foredunes, back dunes, and soakage basins for erosion, vegetation impacts, and any signs of dune instability.

The dune basin is designed to fill during heavy rainfall. Water may temporarily pond near the walkway until it naturally soaks away. Council cannot discharge water through the dunes to keep the walkway open, as this would damage the dunes and breach consent conditions.

They should not cause long-standing mosquito problems. The back dunes drain more slowly because they contain finer sands and organic material, but ponding is usually temporary. Council will monitor the area, but active drainage is not possible without harming dune stability.

This has been considered, but discounted as an option. Modelling shows the northern basin has higher peak flood levels, so connecting them could cause backflow or fail during storms.

Yes. Modelling showed that larger pipes help reduce the duration of flooding, but they do not lower peak flood levels.

The contract for the Seaforth Road stormwater improvements has been awarded to J Swap Contractors, with construction now planned to begin in spring 2026.

This project was originally planned to begin earlier, however taking the time now means we can deliver both the stormwater improvements and road upgrades together. This approach avoids the need to return later for additional works and will deliver better long-term outcomes for the area.

We know that stormwater management on Seaforth Road is a real concern for many in the community. To design the best solution, we’re working with Tonkin & Taylor (T&T) and hapū, who bring important local and historical knowledge of the area, to identify potential improvements as part of the upgrade.

Once options are confirmed, they will be modelled to understand how they perform and any potential impacts. Construction is planned to start in Spring, which allows us to avoid the wetter winter months, when work is more challenging. It also helps ensure the project is completed before the busy summer season, reducing disruption for residents and holidaymakers who use Seaforth Road.

Yes. However, detention tanks would need to be extremely large to make a meaningful difference and are not practical in this environment. Pumping further north is technically possible but would require long pipelines and significant cost.

These options were assessed in earlier investigations, including the 2021 and 2022 Pio Shores stormwater reports.

Wherever possible, we do align roading and stormwater projects, but this was not possible for this project. However, the upcoming Seaforth Road project is one example of where we are upgrading both stormwater and the road at the same time. A dedicated project to assess and improve the south pump station is now underway as part of this project.

Because it sits within the road reserve, Council’s Transportation team is responsible for clearing vegetation, rubbish, and sediment.

It is a Council-owned stormwater asset on private land, so maintenance is shared between Council and landowners. Council is working with local hapū on improvements as part of a wider catchment project.

No. As part of the consent process, the developer had to show that stormwater from the site could be safely managed and would not create downstream impacts. Our Development Engineering team reviewed and approved the design to ensure this.

No. Pump stations are critical infrastructure with strict safety, electrical, and liability requirements. Only authorised, trained personnel can operate them.

The cause of the pump tripping during the January weather event has been investigated and confirmed. It was determined that the issue was due to a failure of a Powerco asset (the power supply to the pump station), rather than a fault with the Council-owned pump station itself. This issue was identified on-site and rectified collaboratively by Powerco and Council staff.

To improve resilience and reduce the likelihood of this occurring again, Council is considering options such as having a mobile generator available in close proximity to provide backup power during similar outages.

For the 25–26 March weather event, our records show that the Papaunahi Pump Station was operating. On 26 March, the pump station operated as designed. The station operates on a duty/assist configuration, meaning that during higher inflows both pumps run together to manage water levels when inflow exceeds the capacity of a single pump.

The Hilltop development naturally drains towards Seaforth Road. During the initial subdivision works, measures were implemented to prevent water from discharging directly off slope faces. Instead, runoff is directed either into the formal stormwater network or conveyed downslope along the natural contours via defined overland flow paths, primarily within the road reserve. Due to slope stability constraints, soakage is not a viable option for managing runoff from this area.

Under normal conditions, stormwater from the Hilltop catchment is directed to the recreation reserve at 34 Bowentown Boulevard, where it is detained and allowed to infiltrate via a constructed stormwater retention pond. However, during heavy rainfall events, when the wider network becomes inundated and water levels rise, overland flow paths can be activated. In these circumstances, some flow may migrate toward the Bowentown Boulevard pump station, although the system is not designed for routine discharge to this location.

The long-term design intent is to provide a more direct and controlled discharge pathway by connecting the stormwater retention pond to the Ōtāwhiwhi Drain outlet. As part of the Seaforth Road upgrade, infrastructure (pipework crossing Seaforth Road) will be installed to enable this future connection. This will allow stormwater to be conveyed away more efficiently and will reduce reliance on indirect overland pathways.

In summary, while the current system can result in some stormwater reaching the Bowentown Boulevard pump station during extreme events, the proposed Seaforth Road upgrade includes works that will better manage Hilltop runoff and reduce loading on the pump station over time.

The pump station upgrade was specifically designed to reduce both the extent and duration of flooding in the area. The key objective of the project was to reduce ponding during a 1-in-10-year rainfall event from approximately 6 hours down to around 3 hours.

To achieve this, several improvements were made to both pump stations:

Increased pumping capacity:

• Papaunahi pump station was upgraded from approximately 21 L/s to 88 L/s
• The second pump station was upgraded from 44 L/s to 83 L/s

Installation of new pump systems:

• Each station now has two pumps (duty/assist), allowing higher flows during peak events.

Larger and upgraded rising mains:

• These allow greater volumes of water to be conveyed away more efficiently.

Improved outlet structures and controls:

• Including orifice plates to manage peak discharge and protect the downstream dune system

Council’s operational records confirm that the pump stations are now operating at their designed discharge rates as stated above, meaning they are performing as intended under normal operating conditions.

It is acknowledged, however, that for approximately the first two years after installation, the pumps were operated at reduced rates. This was a deliberate and precautionary measure to avoid potential dune instability or damage to newly established dune planting. Now that the dunes and vegetation are well established, the pumps have been returned to full operating capacity, consistent with the original design intent.

Based on this, the upgraded system is now achieving the intended level of service and is expected to continue doing so into the future.

It is also important to note that some of the recent rainfall events experienced in the area have exceeded the 1-in-10-year design event that the system was designed for. In these situations, the rainfall intensity and volume can exceed the design capacity of any system, meaning temporary flooding may still occur. In these cases, the limitation is the scale of the storm event rather than the performance of the pump infrastructure.

The delay to the project is to allow stormwater improvements to be fully incorporated into the design. This approach ensures that, once the roading works are completed, stormwater management within the road reserve is optimised and better able to service the area.

It also provides an opportunity to install key stormwater infrastructure within the road reserve that will support future upgrades across the wider catchment. By taking this approach, Council is planning ahead and futureproofing the network to accommodate longer-term improvements.

Importantly, delivering these works together will minimise disruption to local residents. The intention is to undertake a single partial road closure, enabling all required infrastructure to be installed at once. This avoids the need to reopen or excavate the road again in the near future when wider stormwater upgrades are progressed.

In terms of what is proposed, the rehabilitation of the road reserve will proceed as originally planned. In addition, the stormwater component is expected to include upgrades to drainage infrastructure, such as pipes, inlets, and overland flow provisions, integrated into the overall road improvement works.

Council has begun engaging with some neighbouring property owners where land access or infrastructure placement may be required. This engagement is targeted and relates to specific technical considerations.

Broader consultation with the community is now being organised. A community information session has been scheduled for all interested residents and stakeholders to attend:

Seaforth Road Stormwater and Road Upgrades – Community Information Session

Date: Saturday 25 July 2026

Time: 2:30pm – 4:00pm

Venue: Waihī Beach Bowentown Boating & Fishing Club (restaurant area), Pio Road

Public advertising for this event is planned to go out shortly.

Further information about the project is also available on the project web page: https://yourplace.westernbay.govt.nz/seaforth-road

We encourage Pio Shores residents to attend the session to learn more about the proposal and provide feedback. Thank you for your interest and patience as we work to deliver a more comprehensive and resilient outcome for the area.

Council is currently exploring the potential for a second backup or portable pump at the Bowentown Boulevard Pump Station as part of a broader programme of stormwater improvements in the area.

Rather than progressing individual upgrades in isolation, Council is taking a catchment-wide approach to stormwater management. This means a range of potential solutions - including pump upgrades, network conveyance improvements, storage, and alternative discharge pathways - are being assessed and optioneered together to ensure the most effective overall outcome for the network.

The inclusion of a second pump is therefore being considered alongside other interventions to determine how it would best contribute to improving system performance, resilience, and long-term optimisation of the stormwater network.