£1.1 million upgrade of Forest Road reservoir completed
- Guernsey Water's largest treated water service reservoir is now fully operational after a £1.1 million upgrade.
- The upgrade involved cleaning, repairing, and replacing the roof membrane of the 60-year-old infrastructure.
- The project will provide clean drinking water to approximately 10,000 customers.
- Capital Delivery Manager Carl Falla emphasised the importance of ongoing investment in water infrastructure.
- The original schedule for the upgrade was sped up following a water quality test failure in November 2024.
Guernsey Water has successfully completed a significant upgrade of the Forest Road treated water service reservoir, ensuring it continues to deliver safe drinking water to around 10,000 customers.
The £1.1 million investment constitutes the most extensive work on the reservoir in its 60-year history.
The nearly year-long project involved draining 13 million litres of water from the reservoir, allowing specialist contractors to conduct a comprehensive cleaning and inspection of its internal structure. The contractors executed targeted concrete patch repairs on the reservoir's interior.
On the external side, the aging green membrane covering the roof was removed by local contractor Geomarine.
The concrete joints were meticulously hand-filled where necessary, and a stronger, multi-layered waterproof covering was applied.
The roof is now surrounded by wire mesh baskets filled with stone and 1,100 tonnes of gravel, which serves to aid water runoff and provide additional UV protection for the new covering.
Due to weight restrictions on the roof, the gravel was placed using powered wheelbarrows.
Additionally, new rainwater drainage systems were installed, including a collection pond designed to increase biodiversity as part of the project.
Capital Delivery Manager Carl Falla said: "This vital piece of infrastructure has served the island for 60 years and provided billions of litres of water in the process."
He highlighted the importance of the upgrade, noting that targeted network alterations meant customers experienced no disruption during the process. Falla added, "This seven figure investment will future proof the site and ensure it continues delivering for Guernsey."
This reservoir upgrade was part of a larger capital investment programme totalling £6 million in 2025, which included other infrastructure projects aimed at improving network resilience.
Work on the reservoir, originally scheduled for future years, was expedited following a single failure detected in water quality testing in November 2024.
Once the tank was drained, the cause was identified as water ingress via the old roof membrane, leading to the decision to completely replace it. No other failures were detected in the water network.
Falla remarked, "Although undertaking this work in 2025 wasn’t part of the plan, we moved swiftly to reorder the programme and ensured the tank was returned to service as quickly and safely as possible."
He underscored the significance of continued investment in the renewal of water networks to maintain drinking water quality as a top priority, stating that "this is why we test and this is why we invest: to ensure sufficient, resilient infrastructure is in place to provide clean and safe drinking water."
The reservoir measures 55 metres in length, width, and 5.5 metres in height, having been completed in 1965.
No works were performed on the East Tank or Tower during this project, although future investments are planned to maintain sufficient water pressure in the area.
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