InterGroup were engaged by Fonterra to project manage the multi-trade civil and mechanical works for a drainage rehabilitation project at Fonterra’s Clandeboye processing facility. The project involved repairing damaged underground drainage beneath the Weigh Processing Centre, Drier Hall and Evaporator Building, critical assets operating in a high-temperature, chemically aggressive environment.
The works were undertaken during Fonterra’s planned winter shutdown, with a six-week window available to complete the project before production recommenced. While a detailed methodology and programme were developed ahead of the shutdown, the condition and configuration of the buried drainage network could not be fully confirmed until access was established. The delivery approach therefore required ongoing investigation, reassessment and adjustment of repair methods and sequencing as the works progressed.
In 2022, Fonterra Clandeboye commissioned InterGroup to investigate the drains beneath the WPC Plant. The initial CCTV inspection identified multiple major collapses and areas of pipe damage, and InterGroup completed annual follow-up inspections to monitor the deterioration of the assets. Following a further CCTV inspection in 2025, InterGroup proposed pipe relining to address the ongoing drainage issues. Beca, advising on behalf of Fonterra, provided structural input on the areas of the project involving floor slab cutting, including requirements around existing strip foundations and building footings. Beca’s structural advice was incorporated alongside the repair methodology
CCTV inspection identified major damage within the existing drainage network.
What We Did
InterGroup commenced the project with CCTV inspections in 2022 to assess the condition of the existing infrastructure and help identify the areas requiring rehabilitation. Ground Penetrating Radar (GPR), undertaken by a third party, was then used to confirm the location of voids within the plant and help inform the approach to the works. From there, InterGroup took responsibility for the overall project management and coordination of the various specialist subcontractors required to deliver the rehabilitation works.
The project involved a number of interdependent activities, with InterGroup coordinating the decommissioning and recommissioning of process pipework and pumps, concrete cutting, hydro excavation, civil fibreglass repairs, and the subsequent backfilling and concrete reinstatement. CCTV inspections were also carried out before and after the rehabilitation works to assess the condition of the infrastructure and verify the completed works.
As part of the wider project, InterGroup’s Protective Coatings team delivered the floor covering works, bringing the company’s specialist coatings capability into the project. The team also had to adapt to the operational requirements of the plant as the project progressed. At one stage, the programme was accelerated in a particular area so InterGroup could complete the works and exit that section of the plant earlier than originally planned. This required close coordination across the project team and helped minimise the impact on the plant’s ongoing operations.
Developing the solution
Excavation and pipe access works completed within the shutdown window.
InterGroup spent approximately three months developing the initial methodology, using available CCTV information, site information and specialist input to establish a practical framework for delivery. However, the condition and configuration of the buried drainage network could not be fully confirmed until physical access was established. The methodology was therefore developed as a baseline for delivery rather than a fixed construction sequence, with alternative approaches considered where site conditions could not be confirmed in advance.
InterGroup worked closely with its specialist subcontractors throughout the development of the methodology and continued this collaboration during the project as further information became available. Additional investigation was undertaken to better understand the existing drainage network and, importantly, the environment in which the pipework was operating. The drains were carrying both acidic and alkaline waste streams, with pH levels ranging from approximately 2 to 14 and wastewater temperatures reaching up to 82°C. These conditions ruled out the use of a standard internal relining system in some sections and required specialised repair and lining solutions suited to the operating environment.
The investigation and planning process culminated in a detailed 42-page methodology covering the proposed scope of works. PipeMedic was engaged to develop the detailed relining methodology and establish the access requirements needed to complete the rehabilitation works. InterGroup worked closely with PipeMedic to assess and refine these requirements, with the amount of concrete and slab cutting being a key consideration.
The initial methodology identified a number of potential excavation and access points across the site. As the works progressed and further sections of the network were exposed and investigated, the access requirements were continually reassessed. Some planned excavations were able to be eliminated by using existing access points and completing repairs through robotic cutting and relining, while other locations were combined, enlarged or modified to suit the conditions encountered. This approach reduced unnecessary concrete removal and allowed the repair methodology to be adapted to the actual condition of the network.
The project was also constrained by a six-week shutdown window, creating significant requirements around planning, access and sequencing. A key objective was to minimise machinery movement through the plant and avoid the need for a full over-plant access solution. The methodology therefore had to balance providing sufficient access to complete the rehabilitation works with minimising disruption to the facility and maintaining progress within the fixed shutdown period.
The structural integrity of the building was another critical consideration. InterGroup worked closely with Beca and the Fonterra team during planning and throughout delivery to ensure that proposed access arrangements and repair methods did not compromise the building or surrounding structures.
One of the most challenging sections involved a critical pipe located beneath the building foundation and an external silo pad. The original pipe route and surrounding conditions required the team to develop an alternative approach to gain access and reconnect the pipe to the main drainage network. As standard PVC was not suitable for the chemical and temperature conditions in this section, a combination of pipe bursting, fibreglass pipework and specialised chemical-resistant relining was ultimately used. The final solution was determined through investigation and assessment of the conditions encountered during the works, rather than being fully defined before excavation commenced.
Work areas within the Clandeboye processing plant during the shutdown programme.
Delivering the Works
Work mobilised on 8 June within the planned six-week shutdown, with day and evening shifts established to maximise working hours across the programme.
Once the methodology was established, InterGroup coordinated the specialist contractors and site activities required to deliver the works within the six-week shutdown. Tira NDA was engaged as the fitting and fabrication contractor to remove sections of process pipework and motors, providing access to the drainage network. They also designed and fabricated a new style floor drain that allowed InterGroup to future-proof the network and improve access for future maintenance.
InterGroup’s hydro excavation team worked within the factory, excavating from distances of up to 50 metres from the vacuum truck to safely expose the required infrastructure. Three trenching locations were completed, involving approximately 25 m³ of excavation. InterGroup’s civil team carried out the backfilling and reinstatement works, including the use of 40 MPa concrete with a micro silica mix to provide a chemical resistant reinstatement as a second layer of defence for the environment.Excavation and pipe access works completed within the shutdown window.
During the excavation works, the team also uncovered and backfilled a significant void, approximately 3 m wide and 1.5 m deep, beneath an ultrafiltration discharge point. This void was identified by GPR historically, however its severity was not known. Concrete cutting was completed by specialist subcontractor Concut to provide the required access points while minimising unnecessary disturbance to the surrounding structure.
Pipe bursting works to replace the critical section beneath the building foundation and silo pad required careful management of on-site safety. When external ground conditions prevented the hydraulic power pack from being positioned as planned, InterGroup urgently organised procurement of additional hydraulic hoses so the power pack could remain outside the building, avoiding the risk of carbon monoxide exposure inside the plant.
On 17 June, a pipe identified for relining was found to be too badly collapsed to proceed with the planned approach. InterGroup developed an alternative excavation and full fibreglass pipe-replacement methodology within a day, with works starting the following day and no resulting delay to the overall programme.
The programme also remained flexible as the works progressed. Although the Dryer/Evaporator Hall was initially identified as the projected starting point, access requirements and the activities of other projects within the plant led InterGroup to commence in the UF Hall instead. The team then accelerated the works in this area to complete and clear the section earlier than originally planned, allowing the area to be handed over to another project team so they could maintain their own programme. This also helped maintain progress against the wider shutdown programme.
Challenges and Delivery
Before and after: drainage rehabilitation and chemical-resistant relining
The key to securing and delivering the work was confidence in the capability of InterGroup’s specialist subcontractors, supported by strong communication, coordination and project management throughout the works. The project presented a number of significant challenges, including working within an active food manufacturing facility beneath permanently installed, live processing equipment, with the added constraint of a high-temperature, chemically aggressive effluent environment. Access was also restricted in several areas, requiring careful excavation planning around buried chambers and confined sumps. Resources were also temporarily redirected to an urgent pipe repair elsewhere on site during the shutdown, without significantly affecting the overall project deadline.
With a six-week shutdown window, sequencing the various specialist trades was critical to ensuring the project could be completed without extending the plant’s downtime. InterGroup coordinated the activities of multiple contractors, including Concut for concrete cutting and specialist contractors for the pipe bursting and relining works, while also coordinating its own civil and Protective Coatings teams.
Project Results
The project was completed ahead of schedule, with physical works commencing on 8 June and floor covering completed by 9 July, eight days ahead of the original 17 July deadline. The reinstated areas were returned to service within an approximately five-week programme, against the six-week shutdown window allowed, despite design changes, concurrent capital projects on site, and an additional urgent pipe repair in a different manufacturing plant on site.