Project overview
The Loch Ness regional water treatment works project aimed to improve the drinking water supply for Scottish Water customers in Fort Augustus and Invermoriston. The complex multi-site project was delivered by ESD joint venture between RSK Group companies Binnies and MWH Treatment and Galliford Try. The project is part of the Scottish Water SR15 framework agreement, which the ESD joint venture is part of.
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Our role
The Loch Ness water treatment works is a complex, multi-site project representing a multi-million point investment to secure the long-term supply of fresh, clean drinking water for the Fort Augustus, Invermoriston and Glenmoriston communities. A drinking water safety plan identified risks with trihalomethane and cryptosporidium levels at the pre-existing treatment works serving the area. To address this, the project team installed a new single source inlet from Loch Ness and constructed a new water treatment works and associated infrastructure. This included a new raw water intake, new water treatment works, new service reservoirs, new pipelines and new booster pumping stations.
The new water treatment works is located within a forest near Loch Ness, on complex topography and adjacent to the Great Glen Way, one of the most popular long-distance walking and cycling routes in Scotland. Navigating the site and working with local businesses, residents and seasonal tourists would be pivotal to the project’s success.
To serve the communities supplied by the original treatment works, a distribution network system merging two previously separate water supply areas was required. This involved creating two service reservoirs, designing two booster pumping stations and laying a 11 km main for the eastern network. Further installation of a 75-m-long new raw water intake within Loch Ness had logistical and environmental challenges. Disruption to the loch bed and potential contamination from concrete and cement were raised by stakeholders as significant concerns to address.
Working in and near the loch required careful environmental consideration of the impact of activities. To limit below-water construction and reduce concrete use, a novel approach of filling mesh bags with rocks was used for the main intake structure. This created a more natural environment within the loch that would be less disruptive to its natural systems. Disruption was further minimised by assembling the pipes on land and floating them into place using a ballast and precast concrete collars for positioning. Additional silt curtain technology was used to protect the sensitive underwater environment by containing turbidity during the construction process. The design approach of off-site fabrication improved efficiency and control throughout the works.
The new treated water pipeline was designed to follow an existing Great Glen Way track above the A82, which reduced the need to carry out excavations on the road, a critical transport corridor year-round. Where services crossed the A82, work was carried out by horizontal directional drilling. To remove the risk of damage from the new water main crossing the 200-year-old Caledonian Canal, a pioneering hammer-driven auger bore technology was used to mitigate the impact of subsurface voids and variable ground conditions left by the canal’s 19th century builders.
The most environmentally sensitive and visited areas in the Highlands of Scotland
Once installed and commissioned, the new pipeline system has ensured a steady water supply for the surrounding communities and can now cope with seasonal demand. During the tourist season, the daily demand increases by around a third and is growing. During peak periods between March and October, increased demand on the water supply previously led to an almost daily requirement for tankers to fill the existing treated water storage tanks on-site.
The increased capacity provided by the work allows for this growth in seasonal demand and additional growth within the communities. As a result of the upgrades, treated water storage capacity at Invermoriston was doubled to around 0.2 mega litres and more than doubled at Fort Augustus to 0.75 mega litres.
The project won a Green Apple Environment Award for Environmental Best Practice and Sustainable Development in 2020, reflecting the project’s complex and challenging work in one of the most environmentally sensitive and visited areas in the Highlands of Scotland.