Seaview Wastewater Treatment Plant
The Seaview Wastewater Treatment Plant serves a population of about 160,000 in Upper Hutt, Lower Hutt and Wainuiomata. The wastewater is treated or cleaned through a series of screens, tanks, bioreactors, clarifiers and ultraviolet treatments before being discharged into the open sea near near Pencarrow Head / Te Raeakiaki where it is quickly diluted.
A planned programme of maintenance on the Seaview Wastewater Treatment Plant’s main outfall pipeline will commence on 25 May 2026.
These scheduled works will involve a shutdown of the main outfall pipeline that carries fully treated wastewater from the Seaview Wastewater Treatment Plant to Pencarrow for up to six weeks.
The planned works include maintenance on the pipe, pump stations, and related machinery and installations, to support resilience and operation of the pipeline.
The works are being conducted in accordance with our resource consent with the Greater Wellington Regional Council.
Shutdown of the pipeline
For the shutdown and works to occur, the pipeline needs to be emptied. This will involve discharging fully treated wastewater from the main outfall pipe from scour valves along the coastal marine area to empty the pipe for a period up to five days from 25 May.
To keep the pipe empty while the maintenance work is done, fully treated wastewater will also be discharged to the Waiwhetū Stream. There will also be limited discharges of groundwater from at least one scour valve along the coast while the pipeline is empty.
There will be public signage at each discharge location. While there are no expected health, environmental, or odour risks associated with these works, people are advised to please read the signage and refrain from gathering kaimoana/seafood and swimming at the points of discharge.
Planned works
Multiple crews will be operating along the pipeline to expedite the scheduled works, which include:
- entering and inspecting the pipe and fixing leaks as required between the scour valve at Seaview and the scour valve at Windy Point
- replacing parts of scour valves along the pipeline (from Marine Drive to Pencarrow Coast Road)
- asset condition assessments, mechanical parts renewals, sandblasting, painting, and other general maintenance at the pump station and vortex installations at Pencarrow Head
- clearing culverts, replacing manholes, and improving markings along the pipeline
- visually inspecting the pipeline, removing slips and soil around the pipeline, and installing new safety rails south of Burdan’s Gate
- installing new signage at Burdan’s Gate and at the Vortex/Weir installation at Pencarrow Head.
There will be fencing and signage at work sites to protect for the safety of crews and the public.
While the pipeline is emptied, maintenance at the Seaview wastewater treatment plant pump station will also be undertaken.
Traffic management plans
There will be traffic management in place for some of the works. We appreciate the impact of traffic management arrangements on the community and are working with Hutt City Council to finalise a plan to reduce the impact on you. We will provide more information on dates and locations closer to the works starting.
We will provider regular progress updates via emailed customer notifications, Wellington Water’s Facebook page, and this page.
Update 3 - 5 June - Inspecting pipeline from Sunshine Bay back to Seaview
Work is going well, with the pipeline shut down and venting complete. We can now enter and inspect the pipe, and scour valve #1 at the main pump station has been replaced.
Moving into next week, we will continue inspecting the pipeline starting from Sunshine Bay and working back to Seaview. This will require some rolling traffic management, and we may need to return to some sites multiple times. This is due to the fact that identifying faults requires ground water levels to be high enough for them to show. This generally occurs at high tide.
Once inspections are complete, we will repair faults as needed. Timings will be confirmed once the inspections are complete, and we have all the information required.
We will start replacing the manhole pressure lids and installing new seals once the inspection is completed. This will require a similar level of traffic management as required when venting was being completed this past week.
We can confirm that traffic management will be in place next week around Windy Point for 4 days as we excavate and replace scour valve #8.
Works will continue at the end of Pencarrow Coast Road, with the only impact expected to be intermittent noise from the works.
We know that the disruption caused by rolling traffic management can be frustrating, and we are trying to minimise disruption wherever possible. We appreciate your patience and understanding as we continue these important works.
Update 2 - 2 June – Traffic management plans for pipeline inspection works
Last week the main outfall pipeline was shut down and emptied to allow scheduled maintenance on the pipe and related structures to get underway. Maintenance is planned over six weeks through to 5 July 2026.
Pipeline inspection works
Once the pipeline is emptied and is safe to enter, an inspection of the pipeline will be made between scour valve 1 at the Seaview Wastewater Treatment Plant main pump station which is adjacent to the Gough Street intersection and scour valve 8 at Sunshine Bay.
Prior to safe, manned entry of the pipeline, we remove manhole lids and vent the pipeline of gases. We have started this work at the Seaview end of the pipe and will move through to Windy Point by mid this week. For this work we need to put rolling stop-go traffic management in place. Our aim is to minimise disruption to you. Following the works at each manhole, we are installing grated lids that traffic will be able to drive over. We appreciate the inconvenience of rolling traffic management and appreciate your patience and understand as this important work proceeds.
We expect from mid-this week to be able to enter and inspect the pipeline, starting at Sunshine Bay working back to Seaview. This will involve rolling stop-go traffic management as crews enter and exit the pipe.
Once inspection work is complete, we will then repair any faults that are found which may mean more static traffic management for a day or two while repairs are made. Repair work can be undertaken without any excavation.
We will provide updates as the work progresses.
Please call 04 912 4400 or email customer.notifications@wellingtonwater.co.nz if you need more information.
Update 1 - 28 May - Discharge locations
To drain the pipeline this week, we have discharged fully treated wastewater from six scour valves and installed pumps at four locations to allow us to empty the pipeline and keep it empty during inspection activities and repairs. We will also be pumping at York Bay and adjacent to the Marina for a couple of days.
Below is an explanation of the discharge locations and impacts to pathways and roads, under conditions agreed with Hutt City Council traffic management officials.
Work has also started south of Burdan’s Gate. We are engaging with authorised vehicle users about the potential impact on them. Cyclists and hikers will still be able to use Pencarrow Coast Road while the works proceed. Please contact call 04 912 4400 or email customer.notifications@wellingtonwater.co.nz if you need more information.
| Scour valve 2 – 57 Seaview Road, near Barnes Street: There is a shoulder closure of the road at this location and a pump located in the berm by the entrance to the wrecker’s yard. Pedestrians are being diverted into the berm (grassed area). There is little to no impact on road users. |  |
| Scour valve 4 – Sorrento Bay: A pump has been installed at the harbour side of the shared path. Stop-go traffic management using traffic lights will be in place during installation (complete) and removal (date TBC). This will create some delays for road users during this time. This traffic management will be removed and a footpath diversion installed while the site is unattended. There will be some impact to shared path users as the available space for the diversion on the shared path is narrower than normal. |  |
| Scour valve 7 – Sunshine Bay: A pump with fencing and cones has been installed adjacent to the share path on the pump station entrance. The width of the shared path will be reduced slightly to accommodate fencing and cones. |  |
| Scour valve 8 – Windy Point: A pump has been installed on the harbour side of the shared path. The width of the shared path will be reduced slightly to accommodate fencing and cones. |  |
| Scour valve 3 – Marina, Marine Drive: This will be a short-term disruption. There will be stop-go traffic lights in place from Tuesday 2 June to Wednesday 3 June while we empty the pipeline. This may create some delays for road users during this time. |  |
| Scour valve 6 – York Bay: This will be a short-term disruption. There will be stop-go traffic lights in place from Tuesday 2 June to Wednesday 3 June while we empty the pipeline. This may create some delays for road users during this time. |  |
We will provide further updates as the work progresses.
Odour level indicators
The level of odour experienced by the community is influenced by many internal and external factors.
With all these variables, odour can't be forecast with a high level of confidence.
What we can do is monitor the internal factors at the plant which can give an indication of possible odour, and communicate these clearly.
Odour monitors
We've installed odour monitors within the plant boundary and in the community, to capture levels of Hydrogen Sulphide (H2S). You can learn more and view them here.
The health and balance of the plant
Seaview Wastewater Treatment Plant uses a biological process to help treat wastewater, which we work to keep healthy and balanced. This process is complex, with a number of factors. Two of these are Mixed Liquor Suspended Solids and Dissolved Oxygen levels. We use these to help give an insight into how the biological process is managed. We'll update these every month in the graphs below, where green indicates the standard target range for these factors at Seaview Wastewater Treatment Plant. Please note that these ranges are not the same at every treatment plant.
When they are within or close to the target range, it is a good indication that we can expect odour to be at a minimum, unless there is an operational issue at the plant. However, some external factors (i.e. a weather event impacting the flow of wastewater into the plant) may require the team to make the levels higher or lower in order to keep the biological process balanced and healthy.
Plant maintenance and operations
Seaview is an aging plant, with routine operations and maintenance occurring every day, and unplanned urgent maintenance commonly needed to address issues as they crop up. Major project work is intermittent as we continue to address odour and work to upgrade the dryer.
All of these can affect the level of odour experienced by the community, so we work to keep people as up-to-date as possible with all the plant's maintenance and operations. We send notifications to our Interested Parties List, which you can sign up to by emailing customer.notifications@wellingtonwater.co.nz
We also update this page, and our Facebook page with the latest information.
Join the Seaview mailing list
Sign up if you want to receive notifications and updates about the plant - email customer.notifications@wellingtonwater.co.nz
Seaview Newsletter
Find more information about the Seaview Wastewater Treatment Plant activity and projects
Odour Project
Learn more about the ongoing works to reduce odour at Seaview Wastewater Treatment Plant
Odour monitors
Check out the Seaview odour monitors and learn more about odour here.
Making a complaint
If you have a complaint about Wellington Water directly, please call 04 912 4470 or email customer@wellingtonwater.co.nz to access our free complaints process.
After hours, please contact the Hutt City Council Call Centre on 04 570 6666 / 0800 488 824.
Greater Wellington Regional Council is the regulatory agency for reporting airborne discharges 0800 496 734.
Complaints to the Seaview Wastewater Treatment plant can be sent to the following contact details:
First point of contact: Veolia Duty Manager - Call 0800 928 371.
Veolia's Duty Manager contact number operates 24/7 as such complaints can be directly forwarded to them especially if the complaint is urgent and/or happened after office hours.
When a complaint is received, the following information will be recorded:
- Name
- Contact details of the customer
- Nature of the complaint
- Date and time
- Location
Complaints shall be actioned within 24 hours upon receipt and the records being written to the plant's operational incident log. Odour and/or wastewater discharge complaints will be forwarded to the regional council.
Plant performance
Current status: Non-compliant
Period: March 2026
Commentary:
The plant is compliant for both suspended solids and biochemical oxygen demand. Faecal coliforms remain non-compliant.
Discharges:
There were no unauthorised discharges in March. An emergency repair to the main outfall pipeline was required, see items of significance for more detail.
Odour Complaints
There was one odour complaint received in March.
Items of significance:
Effluent compliance: The plant became compliant for suspended solids in March. Faecal coliforms results are improving but occasional spikes in daily results continue to affect the parameter averages and delay a return to compliance.
Seaview Main Outfall Pipeline (MOP) repair: A leak was discovered on the MOP in March. The repair required a full drain down of the pipe allowing the team to enter and carry out the repair to the joint seal. During this time, fully treated effluent was discharged through the Waiwhetū Stream.
Odour Treatment Project
The new milliscreen building odour treatment system was fully commissioned in December and main project works completed.
What’s coming up:
- Installation of the final community odour monitor.
- Independent assessment of the effectiveness of the Odour Control Project – Stages 1 and 2.
Read all the Seaview wastewater treatment plant monthly performance reports
Resource consents
WGN050359 [39668] Discharge Treated Wastewater to Coastal Marine Area (Seaview WWTP)
WGN050359 [24539] Discharge Treated Wastewater to Coastal Marine Area (Seaview WWTP)
WGN120142 [31740] Construction to Coastal Marine Area Maintenance (Seaview WWTP)
WGN120142 [33406] Discharge of Treated WW to Fresh Water Wet Weather (Seaview WWTP)
WGN120142 [33407] Discharge of Treated WW to Coastal Marine Area Maintenance (Seaview WWTP)
WGN120142 [33408] Discharge Treated Wastewater to Stream (Seaview WWTP)
WGN930193 [1] Contaminants Discharge to Air Outfall Structure (Seaview WWTP)
WGN930193 [2] Contaminants Discharge to Air Venting Structure (Seaview WWTP)
WGN950162 [1] Contaminants Discharge to Air WWTP (Seaview WWTP)
WGN930194 Land Occupation by Outfall Pipeline and Structures (Seaview WWTP)
Compliance reports
Seaview Wastewater Treatment Plant - 2021 2022 Compliance Report
Seaview Wastewater Treatment Plant - Consent Compliance Report 2022 - 2023
Seaview Wastewater Treatment Plant - Consent Compliance Report 2023 - 2024
Resource consent reports
Annual Reports:
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2024/25
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2023/24
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2022/ 23
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2021/2022
Seaview Wastewater Treatment Plant Annual Resource Consents Report 2020/2021
Seaview Wastewater Treatment Plant and HCC/UHCC Trunk Main Annual Resource Consents Report 2019/2020
Quarterly Reports:
Seaview Wastewater Treatment Plant - January - March 2026 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant - July - September 2025 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant - January - March 2025 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant October - December 2024 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant July - September 2024 - Quarterly Resource Consents Report
Seaview Wastewater Treatment Plant January - March 2023 - Quarterly Resource Consents Report
Appendices:
Appendix IV - Annual Resource Consents Report - Hutt Valley Tradewaste Report 2024/25
Appendix V - Annual Resource Consents Report - AEE Waiwhetu Stream Wet Weather Discharges 2024/25
Appendix VI - Annual Resource Consents Report - AEE Non-compliant Discharges 2024/25
Seaview Wastewater Treatment Plant Annual Consents Report 2023-24 - Appendix ||| Trade Waste
Public health statements on the use of the treatment plant odour neutraliser
Summary
Potential health concerns associated with exposure to quaternary ammonium compounds are most likely associated with direct contact with undiluted product i.e. the staff preparing the solution. Staff exposure risk is managed by following the correct health and safety procedures. Quaternary ammonium compounds are often part of household cleaning and disinfection products and so exposure to the public is relatively common. Given the level of dilution of the product used in the cannon, and the distance between the placement of the cannon and potential locations for public exposure (typically this type of cannon dispersal method has an estimated droplet range of 50-100 metres) that effectively dilutes the strength further, we would not expect this to represent a health risk for the general public.
Te Whatu Ora - Health NZ - April 2023
_________________________________
In May 2024, The plant operator, Veolia, switched to a new product Odour Neutraliser Plus (SCD1100) which is manufactured by biOx Environmental. This is a stabilised chlorine dioxide product that oxidises odour molecules such as Hydrogen Sulfide. The product is safe when used as directed and is utilised in wastewater treatment plants, landfills and transfer stations throughout New Zealand. While the previous product Hi Chem Disinfectant Reodorant presented no public health risks (see above) we decided to act on complaints from the community about the odour it generates and changed to Odour Neutraliser Plus (SCD1100). More information about this product
Independent assessment on the impact of the odour neutralisers
Regarding any impact of the odour neutralisers, an independent assessment has been undertaken and the report concluded that the potential health risks regarding the use of the odour deodorisers are low and acceptable in accordance with New Zealand Guidelines. A copy of the report can be found here.
Odour Investigation Reports
Seaview Wastewater Treatment Plant - Odour Deodoriser - Air Quality Assessment - October 2024
Seaview Wastewater Treatment Plant - Odour Investigation - June 2023
Seaview Wastewater Treatment Plant -Biofilter Flow Assessment -March 2024
Community Liaison Group
Consents
One of the nine resource consents permitting the operation of the plant, consent ‘WGN120142 [33408] Discharge Treated Wastewater to Stream ' expired in 2018.
Prior to the expiry of this consent, Hutt City Council applied to Greater Wellington Regional Council (GWRC) for a new consent to temporarily discharge treated wastewater to the Waiwhetū Stream.
While the reconsenting is underway, we continue to operate under the existing consent.
In general, the consents allow Hutt City Council to:
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discharge treated and partially treated effluent through an existing outfall,
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discharge mixed disinfected, treated and milli-screened wastewater during and/or immediately after heavy rainfall,
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discharge mixed disinfected, treated and milli-screened wastewater during maintenance,
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discharge of contaminants to the air, and
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to occupy the stream and coastal marine area with an outfall structure.