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Completed Projects

We are excited to share the completion of one of our wastewater infrastructure projects! Here’s what you need to know:

🚧 Scope Completion:

  • The initial contract scope has been successfully completed and reinstated.

🔧 Additional Work:

  • We allocated additional scope for replacing the mains on Knowles Crescent.
  • Approximately 260 meters of mains has been replaced across four sections in Knowles Crescent.

We applaud South Roads for their outstanding work and timely completion of work on this crucial project.

Thank you for your patience and support as we enhance Ranfurly’s wastewater infrastructure! 💙

For more information see Improvements to Ranfurly’s wastewater resiliency begin - Central Otago District Council (codc.govt.nz)

We’re thrilled to announce the successful completion of a crucial project in our water infrastructure. Here’s the scoop:

🚧 Project Overview:

  • Our wastewater pump station sites have undergone upgrades.
  • The addition of generators ensures that during power outages, these sites are no longer vulnerable to emergency overflows into nearby rivers and lakes.

🌟 Upgraded Pump Stations:

  • Alpha Street
  • Melmore Terrace
  • Wrightson’s (Opposite Linger & Die Reserve)
  • Bridge Hill

Next time you drive past these locations, take a moment to appreciate the enhanced resilience of our wastewater system!

Current generator outside Lake Dunstan Water Plant

Melmore and Alpha Street Generators

Completed! This contract was awarded to SiteCare Ltd and was completed over the past 5 months.

The two wastewater ponds at Roxburgh underwent desludging with a dredge, and the extracted sludge was subsequently pumped into geo bags on the site.

Desludging of the ponds is an important maintenance activity for waste stabilisation ponds, as sludge accumulation reduces treatment capacity and can result in an increase in odour emissions.

A pyramid of geo bags has been established at the treatment plant site. These bags will remain in place for about 12 months or until they achieve the necessary level of dry solids, after which they will be disposed of.

Across towns in Central Otago, the water network is aging and showing signs of potential failure in the form of bursts and leakages.

A list of pipes with the highest priority for replacement was developed and following a tender process in April 2023, the contract to replace watermains within the Roxburgh township was awarded to Fulton Hogan Ltd.

Works commenced in July 2023 replacing the watermain in Scotland Street and was completed in March 2024. Local residents were very patient and helpful during this project.

Main on Smith Street being installed

New lateral water pipe being replaced outside St John

The old pumpstation was situated in the middle of Earnscleugh Road and caused considerable risk to operational and maintenance staff and was not constructed to the required standard for access.

Council constructed a new pump station and then connected to the reticulation system. The new pump station was installed, commissioned, and brought into operational service during February 2024.

Images of completed pumpstation

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Background information

Originally consulted on with the community in the 2018 Long-term Plan, the Lake Dunstan Water Supply project is getting close to going live at the end of May 2023. The $16.1 million upgrade to the water supplies of both Alexandra and Clyde reflect our focus on the health and wellbeing of our communities.

The project scope included the expansion of the Clyde bore field and the construction of a membrane treatment plant and water storage tanks now complete.

You might be aware of the benefit this upgrade will provide by reducing the lime in Alexandra’s water, but you may have questions about the membrane treatment. The membrane treatment provides an additional level of treatment, along with chlorination. The upgrade in treatment process will ensure we continue to provide safe drinking water to the community, and we meet our responsibilities against the New Zealand Drinking Water Standards.

The changes to the terrain involved with the water treatment upgrade add to the history of changes in the area to advance the community.

In comparison to the above, the two images below show how much the area has changed over the last 40 years.

Bore fields

The photographs taken in 1978 and 1981 respectively, indicate where our extended bore field now sits.

Photo from Thompson, R., 1991a. Clyde Power Project: Dam left abutment to Clyde groundwater. Letter report from DSIR Geology and Geophysics to Works Project Services, 14 May 1991. Taken by Homer (1978).

Photo from Thompson, R., 1991b. Item No.102, Foundation – Part 1, Excavation, Associated Remedial Work and Diversion Construction Report. Preliminary draft for comment. DSIR Report. Taken February (1981).

Three bores on the edge of Lake Dunstan will supply the treatment plant feeding Alexandra and Clyde. The installation of a new bore and the upgrade of a second, brings our borefield in line with new water safety regulations. The existing bore currently feeding Clyde will be upgraded once the treatment plant is commissioned in April 2023. The upgraded bores will be able to pump water to the raw water tank up to 160L/sec.

Our investment in the upgrade of our borefield ensures we provide safe, healthy and clean water to our community.

Left to right: Completed bore with new above ground design and flow meter. Upgrades to the second bore through September.

The unique design of the removable roof on the borefield building has paid off. The images below show the switchboard installation in September. Designing the building in this way meant that we could continue with the build while we waited for the switchboard to be constructed.

The unique design of the borefield building allowing for the roof to be removed for the installation of the switchboard in September.

Lindavia

Like any major project, it has not been without its major challenges; the discovery of the algae Lindavia in Lake Dunstan, and the onslaught of the Covid-19 pandemic in 2020 causing delays. Read about Lindavia below.

The unexpected discovery of the algae Lindavia in the lake, and the need to undertake trials to ensure filtration as required under the Drinking Water Standards could efficiently and affordably be achieved, Lindavia would not only have blocked the filtration system proposed before the trials, but would also have blocked people’s home irrigation systems, so this was a good problem to find out about early on in the piece.

Progress July - September 2022

Reliant Solutions completed the construction of the raw water tank on site at the end of August 2022. The pre-treatment tank at 350m3 in size, allows for the control of flow through the membrane treatment plant.

Raw water tank at its full height end of August.

The internal slab was completed in late August with the construction of the control room, chemical bund, staff amenities, loading bay and analyser room all completed within the last month.

The switchboard, weighing an impressive two tonne (that’s the equivalent of approximately 20 baby elephants!) was installed in mid-September.

Construction on the treated water tank commenced in late September. The treated water tank holds 750m3 of water and feds Clyde and Alexandra. The tank is approximately 20m higher than the Alexandra Northern reservoir, so can fill the tank by 100% gravity with no pumping required – a great efficiency.

Left to right: Construction of the treated water tank through September and October 2022

The end of September 2022 saw the pouring of the plinths ready for the delivery of the three membrane racks due in late November. Throughout the planning and build, efficiency and resiliency have been kept front of mind. With predicted growth in the district, by 2028, it is expected that we will need to upgrade the number of membranes. In preparation for this, we have extra plinths ready to go.

Smart building and resiliency have continued through the construction with the installation of generators at both the treatment plant and the bore field. The generators will kick in within two minutes of any power outage, ensuring a reliable water supply, no matter what the conditions.

The roof, walls and roller doors have been constructed with insulation to ensure that we keep the equipment, and our people, warm in the winter and cool in the summer. To keep the electrical components at a cool temperature through the heat of the summer, the team selected modern air-cooled scroll chiller units, for the high energy efficiency and sustainable benefits.

Top left – top right: July preparation for slab. Reo steel placed for slab to be poured.

Bottom left- bottom right: Late August floor slab poured. Mid-September – installation of the membrane plinths and the switchboard.

June through to October saw the cladding of the exterior of the treatment plant building and the completion of the delivery bay ready for the arrival of the membranes.

Progress of the retaining wall along the south-western side of the treatment plant.

The pipe work and valves have been installed between the treatment plant and the treated water tank. Bypasses have been included throughout the site to allow for resiliency through any emergencies.

Mid-September – Pipework being installed between the treatment plant and the treated water tank.

Progress October 2022 - May 2023

In January 2023, a large generator was delivered to the site. Our generators will kick in within two minutes of any power outage, ensuring a reliable water supply, no matter what the conditions.

The building at the Water Treatment Plant on the hill above Clyde has been completed. This timelapse video shows installation of the three membrane racks at the water treatment plant on Clyde Lookout Road (pictured below).

Membrane filtration is a rapidly expanding field in water treatment. Membranes are used to remove undesirable components from water, such as Giardia and Cryptosporidium. At our Water Treatment Plant in Clyde, the membranes are loaded into racks. Each rack holds 80 modules, and each module encases 6350 fibres. This means there is 50 square metres of membrane area per module.

The final touches to the water treatment plant are now underway including the planting of 500 native trees and shrubs around the plant that took place in April. The bunds at the water treatment plant have also been hydroseeded with silver tussock seed mix. Hydroseeding involves combining water, premium grass seed, fertiliser and wood mulch fibre to provide a microclimate that encourages germination and helps to prevent soil erosion and bird damage. Pictured during planting are Water Services Team members Yuval, Duncan and Alex.

Irrigation work is being carried out around the treated water tank site. Water will be reused from the treatment process, which gives the plants - natives having been used - the best chance to thrive, while softening up of the bund area.

Official opening and blessing: June 2023

Three Waters Director Julie Muir and Mayor Tim Cadogan (centre) and Capital Projects Manager Patrick Keenan taking the first sip.

The Lake Dunstan Water Supply went live from 23 May and was officially blessed and opened on 22 June at the Lake Dunstan Water Supply treatment plant at Clyde.

As the new water supply for Clyde and Alexandra moved through the transition phase from the old system to the new, people enjoyed a new and improved water supply that also meets the new NZ Drinking Water Standards.

Pictured above are a very happy Water Services Team toasting their success with a special taste test to kick it all off.

Public enjoy a good day out at Lake Dunstan plant open day - Central Otago District Council (codc.govt.nz)

Pictured below, staff and contractors welcoming visitors to the open day.

A new reticulated wastewater system will replace Clyde's existing system which relies on septic tanks and disposal fields. The upgraded system will meet environmental and resource consent requirements, significantly improving the quality of Clyde's urban wastewater discharges.

Importantly, it will provide the Clyde community with an environmentally safe wastewater system that will bring significant environmental, health and well-being benefits for decades to come.

The project is being completed in three stages spanning. The first stage has now been completed, while two further stages which cover the remainder of the town are scheduled for 2028-33 and 2038-43.

Stage one included installing a wastewater pipeline, a pump station and the new reticulated wastewater system for central Clyde.

The image below, provide an overview of the recent work involved in this project.

Installation of connections and low-pressure pump systems on private property.

Pump Station at Miners Lane completed

Reinstatement work on private and Council properties in Clyde

Download the map below to view a detailed map of Stage one of the Clyde Wastewater Reticulation project.

If you have any questions about the Clyde Wastewater project our team would be happy to answer them! Just email waterprojects@codc.govt.nz

E-newsletter links

Read media releases on Clyde projects

Progress through May 2023

The Clyde Main Wastewater Pump Station was fully commissioned on 13 December 2022.

This $3.4 million project is a key component of the Clyde wastewater reticulation system. Clyde’s wastewater will be gravity feed from the township through two smaller pump stations before reaching this main pump station off Sunderland Street adjacent to the Clyde dog park. This pump station will then transport the waste through to Alexandra for treatment.

This project provides infrastructure to support growth and will contribute to improved water quality in the Clutha Mata-au.

Progress through October

Through the last week in October and early November the commissioning of the Clyde main wastewater pump station is being carried out.

The commissioning is a multi-stage process that systematically works through each process within the pump station to ensure correct operation before the go live date.

The commissioning included the installation and testing of the two pumps into the well. The pumps, at 55kw each, will work one at a time to pump the wastewater from Clyde to Alexandra at 69 litres per second. The well is 8m deep and 3m wide and will control the flow of wastewater from Clyde through the pipeline to the Alexandra wastewater treatment plant.

Other processes being tested through this phase of the project include the odour controlling chemical dosing unit, instrumentation and telemetry, connection with the Alexandra pump stations, the generator, valve operation, the operation of the emergency storage tanks, and the priming of the 8km wastewater pipeline from Clyde to Alexandra

The completion of the commissioning will allow for the final connections to be made to the properties and stage one of the wastewater system to go live.

Commissioning of the Clyde main wastewater pump station. Pumps being installed into the 6m deep wells.

The completion of the renewal of the Clyde Falling Main through April and May was an important achievement.

Funded by the Central Government Water Stimulus package, the $1,050,000 project, replaced the existing gravity-pressured water main, a critical piece of infrastructure for the Clyde water network. The falling main supplies water from the reservoir, at the top of the hill, down to water mains at Sunderland Street.

The original falling main, constructed in 1987, was identified as having several issues that presented a risk to a resilient water supply in Clyde. The pipe material was identified as having poor seismic resilience and due to the steep terrain, effective maintenance and repair on the aging pipe was difficult.

This work will ensure that we continue to provide safe and reliable water to Clyde.

To create efficiencies across projects, three other pipelines were installed in conjunction with the falling main upgrade. Two pipes from the Lake Dunstan Water Supply and one from the Clyde Wastewater Reticulation project. We’ve invested our ratepayers' money effectively at the right time to ensure a positive outcome for the community.

CODC and its contractors have been busy with the replacement of the 100-year-old watermain along Centennial Ave in Alexandra.

This pre-emptive work occurred prior to the pavement renewal planned by Waka Kotahi later this year.

Work involves installing new stormwater drainage pipelines from standalone drainage sumps and soak pits to the existing reticulated network, thus improving stormwater drainage during high rainfall events.

As part of your Council's commitment to reduce the environmental impacts from urban wastewater discharges, we are upgrading two wastewater pump stations in Alexandra. The first in the Linger and Die Reserve adjacent to Walton and Rivers Streets, with upgrades to the Dunorling Street station to follow.

Both projects include the connection of the Clyde wastewater reticulation system to the Alexandra treatment plant and increase the emergency storage capacity of each station. The emergency storage ensures that we have storage capacity within the stations during any unplanned outages.

Progress through October

At the Wrightsons Pump Station, which is in the Linger and Die Reserve, the Fulton Hogan team has installed the underground tanks and completed the welding and electrical work.

This was then backfilled and reinstated, the grass will be seeded in the upcoming warmer months.

The commissioning of the Clyde main pump station is closely linked with the Wrightsons Pump Station. Ensuring the two assets are synced with each other is an important step.

The storage tanks for the Dunorling Street pump station upgrade have been ordered with delivery expected in early 2023.

Ensuring the protection of the flood bank and the restoration of the local area is an important part of all our projects. We gratefully thank the community and local residents for their understanding throughout this important project.

Wrightsons Pump Station construction.

Pictured above the tank sections being craned in.

Progress through May - June 2023

Now that the Wrightsons Pump Station emergency storage units have been completed, Fulton Hogan have commenced (and nearly completed) installing a similar emergency storage unit at the Dunorling Street Pump Station.

The Dunorling Street pump station takes wastewater from the entire Alexandra and Clyde network (including Wrightsons pump station) and pumps it to the Alexandra Wastewater Treatment Plant. The emergency storage units ensure that we have storage capacity within the stations during any unplanned outages.

Prior to the installation of the storage unit, should the pump station go fully offline, there was only approximately a one-hour response time before wastewater would flow into the Clutha River/Mata-Au. However, the Dunorling Street storage unit increases the response time to eight hours, thus adding further resilience to the wastewater network. Additionally, this capability adds another layer of safety to perform maintenance works at the pump station and downstream Alexandra Treatment Plant by redirecting the wastewater to the emergency storage unit when necessary.

By clicking on this link, you'll see a series of photos showing the Dunorling Street storage unit being constructed, featuring 17 reinforced concrete sections. The tank itself is 25m long x 3m wide x 2m high. Once completed the whole unit can contain up to 150 cubic metres of wastewater.

Drone photo of storage installation

Dunorling Street final stages

All earthwork on the site is completed, reinstated and hydro-seeded. The storage tank is commissioned and was handed over to the Operation Team on 1 June 2023.

The area is still fenced off for public access with environmental control measures and an alternative route for pedestrians and cyclists in place to provide enough time for the grass to re-establish and stabilise the ground. We are expecting this will help to establish the space for community use before spring and we'll be letting people know when this will be.

There will be some finishing mechanical and electrical work going on in the next four to six weeks.

The construction of the reservoir will feed clean, safe water to Alexandra from the Lake Dunstan Water supply. Funded through Water Stimulus funding, the $2.8 million construction of the 4000m3 tank holds nearly enough water to fill two Olympic pools. The reservoir will be filled and commissioned when the Lake Dunstan Water supply project is completed in 2023

The reservoir will provide storage of treated drinking water for Alexandra for 10 hours during any periods of unplanned outages. We’re committed to improving the resilience of our local water so that everyone in our community benefits.

Progress through October

Fulton Hogan crews have completed the pipework that will connect the new reservoir tank to the main pipes laid at the bottom of the hill.

Reliant Solutions will be back on site through November to carry out leak testing. Leak testing consists of filling the tank to ensure there are no issues before the Lake Dunstan Water Supply go live date in April 2023.

During the construction of the new reservoir, resilience has been built in through the inclusion of valves to maintain flows through any required maintenance and an onsite generator for any unexpected power outages.

The unique construction of the tank can be seen in the time-lapse video capture by our contractor.

The old reservoir (front) and the new reservoir (rear)

The drying bed area of the Alexandra Wastewater Treatment Plant was particularly vulnerable to erosion from a naturally occurring stormwater flow path that flows through the length of the treatment plant site, especially at risk during high rainfall events.

This project involved ensuring the protection of the walls from erosion around the plant’s drying bed area and clarifier.

Stage 1 commenced in early 2022 and Stage 2 continued in July 2023 with the construction of the rock erosion protection walls. This was a continuation of the Stage 1 work already completed past the clarifier (an essential step in a wastewater treatment process involving removing suspended solids through gravity settling, thus providing a clarified liquid effluent).

Construction of the erosion protection rock walls

Following issues with the stormwater pipes negatively impacting private properties in Hawkdun Place, Alexandra, work is almost complete on remedying the stormwater systems in this area.

This has included undertaking CCTV footage of the existing pipeline, the installation of new sumps and pipework, and the installation of a surface mounted kerb along the uphill side of the road.

Following road resurfacing, the plant and equipment was disestablished and the project formally completed on 30th June 2023.

Pavement reinstatement ready for asphalting

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