Moa Point wastewater treatment plant refurbishment projects
We're refurbishing the Moa Point wastewater treatment plant inlet pump station and a clarifier, on behalf of Wellington City Council, to increase resilience and reduce the risk of discharges. Click the background tab to find out more.
If you have any questions about this work, please contact:
Wellington Water, 04 912 4400
Latest Updates
The inspection of the clarifier has been completed with the specialist engineers identifying some areas needed for additional remedial works.
Works are underway to clean the wet well at the Moa Point Inlet Pumping Station ahead of the 2 riser pipes replacement in April. This may increase the level of odour around the pumping station whilst this cleaning is carried out.
In preparation for the inlet pump station work that's coming up, we've provided residents with more information via the resident letter last week.
Works on the first phase of the refurbishment to replace four of the 10 riser pipes in the IPS are now complete. The next phase of work to install 2 new riser pipes in the adjacent wet well is expected to begin in late March 2024.
Please see the Updates tab for more detailed information on the progress of the works.
The inlet pump station and clarifier projects are being undertaken in parallel to shorten the time that the treatment plant’s capacity is reduced. Work on the clarifier starts on 15 January 2024.
This project is not associated with current works underway at the treatment plant constructing the new Sludge Minimisation Facility (SMF).
Why is this work needed?
Some of the electromechanical parts, pipework and pipe fittings in parts of the treatment plant are reaching the end of their design life.
The refurbishment programme will replace and repair these parts at the inlet pump station and one of the three clarifiers. This will increase the resilience of the pump station and improve environmental and health outcomes by reducing the risk and frequency of discharges through the short outfall into the environment.
Veolia, as operator of the Moa Point wastewater treatment plant, will undertake the works which are being done in several phases.
Here are more details on the inlet pump station and clarifier refurbishment projects.
Inlet pump station
The first phase of the refurbishment programme involves replacing four of the 10 risers at the inlet pump station to help address the immediate risk of discharges to the environment while the rest of the refurbishment project is completed.
Works on this first phase started in early October 2023 and are expected to be completed by 24 November - subject to any wet weather.
The long-term plan is to replace all 10 risers and pumps n a phased programme that will restore the plant’s design pumping capacity of 4,000 litres per second. The programme is expected to take between 12 and 18 months to complete.
This work requires careful planning and execution as the riser pipes are large and heavy, requiring specialist lifting equipment and personnel to complete the work whilst operating in a hazardous environment.
We are still finalising the next phase of works, but it is broadly planned to commence in early 2024. It will be undertaken in conjunction with other planned work at the plant to minimise disruption to operations.
We will provide updates as soon as we have finalised the work programme.
Clarifier
The Moa Point wastewater treatment plant has three clarifiers. These are large tanks that are used to separate the large clusters of bacteria called sludge from the treated wastewater through gravity.
One of the major mechanical components of one of the clarifiers, the clarifier bearing, is at the end of its life and needs to be replaced. Doing this requires the clarifier to be taken offline. The work is being undertaken proactively to avoid plant failure which would cause unconsented discharges from the treatment plant.
Having one clarifier offline will temporarily reduce the plant’s capacity from 3,009 L/s to approximately 2,000 L/s. That is why we are doing this work during summer to autumn when there are lower flows.
We are confident the plant will be able to treat dry weather flow levels with the remaining two clarifiers. However, the reduction in treatment capacity does increase the risk of unconsented discharges of partially treated wastewater at the long outfall during periods of high rainfall although this risk is assessed as low overall compared to undertaking the work during winter.
Emptying and cleaning the clarifier will involve removing some sludge, which may cause a very low amount of odour, but it will only be for a short period.
This work is due to be completed by June 2024.
Wellington Water will provide regular updates regarding this project.
All Updates
The inspection of the clarifier has been successfully completed with the specialist engineers identifying some areas needed for additional remedial works.
Examples identified were corrosion around various bolts and brackets (Image 1) that help support the internal structure. These will be replaced along with other key steel structural supports that may require cleaning/recoating to protect against future corrosion (Images 2 & 3).
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| Image 1 - Corroded bolts | Image 2 - Minor corrosion to support beams | Image 3 - Steel structure to be recoated |
These physical works are now underway and will precede the main upgrade to the key mechanical components of the clarifier in the coming weeks.
We will keep you informed as the project progresses.
Works are underway to clean the wet well at the Moa Point Inlet Pumping Station ahead of the 2 riser pipes replacement works in April. This may increase the level of odour around the pumping station whilst this cleaning is carried out.
The physical works to replace the riser pipes will begin on 3rd April. Once completed, this will bring the total to six out of the 10 riser pipes replaced, significantly improving reliability and resilience against short outfall discharges to the Coastal Marine environment.
The works involves taking one of the two wet wells offline throughout the duration of the project. We are confident that one wet well will be able to handle the dry weather flow going into the inlet pump station. However, the temporary reduction in the pump station’s discharge capacity does increase the risk of untreated wastewater overflows to the short outfall during a period of heavy rainfall. This project is being undertaken in parallel with the Moa Point Wastewater Treatment Plant clarifier refurbishment project to reduce the timeframe of the plant operating at reduced capacity. The Inlet Pumping Station project is expected to be completed in May 2024 with the clarifier works finishing in June 2024.
Should there be an overflow at any time during the Inlet Pumping Station project work, we will immediately notify the community as per the standard protocol.
In preparation for the second phase of the inlet pump station work that's coming up, we've provided residents with more information via the Resident letter - Moa Point Inlet Pump Station Phase 2 which was posted last week.
This work will commence at the end of March 2024 as part of a wider programme to refurbish the station. We'll keep you informed as the project progresses.
Contractors have completed the cleaning of the inside of the clarifier.
All the components are now ready to be structurally assessed by specialist engineers and these inspections are scheduled for next week, weather permitting.
After the inspections are completed, the team will begin the planned upgrade works to the main mechanical components of the clarifier and also any potential additional remedial works discovered through the inspections.
We will keep you informed as the project progresses.
Good progress has been made by the contractors who have been power washing the inside of the clarifier these past few weeks (see pic below).
This has enabled some extra scaffolding to be erected which will allow the contractors to access the areas that are inherently more difficult to clean.
Once this more detailed cleaning to expose steel and mechanical components is complete, the clarifier will then be ready to be structurally assessed by a specialist engineer. This inspection will hopefully take place around the beginning of March.
We will keep you informed as the project progresses.
(Inside of Clarifier 2 post initial clean)
The team have drained down the clarifier last week.
This is the first stage of a large project that will see the inside of the clarifier cleaned, refurbished and re-painted before a full replacement of the central mechanical bearing that drives the scrapers around the structure. There is a chance this may cause minimal odour but it will only be for a short period.
This now enables the contractors to safely enter and begin power washing the whole inside of the clarifier. This process will begin this week and is expected to take around 3-4 weeks.
Once the cleaning is complete it allows a structural engineer to accurately assess the condition of the clarifier and identify any potential remedial works needed.
We will keep you informed as the project progresses.
Please be advised that the draining down of the clarifier has been rescheduled to next week, from the 23rd January 2024.
This extra period will be used by the operators to ensure the plant is in optimum condition to have the clarifier taken ‘offline’ ahead of the project.
Thank you for your patience and understanding.
From 15 January 2024 we will be starting work on refurbishing one of the three clarifiers.
This project is being undertaken in parallel with the replacement of the rising main pipes at the inlet pump station to shorten the time that the treatment plant’s capacity is reduced. It involves emptying and cleaning the clarifier and having it assessed internally by structural engineers. The team will then begin the process of installing the new main drive and bearings. Click on the background tab to find out more about the 'clarifier' project.
Emptying and cleaning the clarifier will involve removing some sludge, which may cause a very low amount of odour, but it will only be for a short period. We will provide further updates about the exact timing of this work.
We are delighted to inform that the 4 pumps were successfully reinstalled this week and the wet well was back brought back online from Tuesday - 3 days ahead of schedule!
Veolia have been monitoring the pumps performance closely over the last few days to make sure the desired performance, from both the pipes and pumps, is being achieved.
The next phase of works for Inlet Pumping Station will be to install 2 new riser pipes, just like the 4 installed this month, in the adjacent wet well. These works are expected to begin late March next year.
Last week’s work to fix the wall brackets and anchors was successful and we are pleased to report the riser pipes are now fixed in their positions, ready to be connected to their individual pumps.
The scaffolding within the wet well has been removed and the contractor brought in to install the riser pipes has now demobilized from site.
This week Veolia began the process of reinstalling the 4 pumps and this is expected to be finished by the end of the week.
We will provide another update next week and confirm the status of the project.
Works are progressing well at the inlet pump station with the 4 riser pipes now in position.
This week will see the installation of the wall brackets and anchors to keep the pipes fixed in their position as well as some minor grouting within the wet well.
Assuming this work goes to plan, we plan on lifting the 4 pumps back into their original positions the following week.
We will provide a further update when this week’s work has been completed.
