Screen upgrades at Tyndrum Wastewater Treatment Works, Scottish Highlands

Project summary

Upgrades to Tyndrum Wastewater Treatment Works’ screening process have enabled its capacity to triple from 3.2 litres per second to 10.6 litres per second. From December 2024 to July 2025, WGM Engineering delivered the project through design to commissioning for Scottish Water, keeping to tight time frames and overcoming structural challenges.

The background

Tyndrum Wastewater Treatment Works is located next to the West Highland Way in Tyndrum at the foot of the Scottish Highlands. The village has a small population, which is economically dependent on the summer tourist season.

Scottish Water required the plant’s screening process to be upgraded to improve its capacity and operational efficiency. Screening is the first stage of wastewater treatment, which removes large debris and waste from the water through a filter. To ensure no disruption during the summer season, the work needed to be completed before tourists began to arrive in July. This gave a window of seven months from December 2024 to deliver the design, build and commissioning of the concrete channel and screening units.

To deliver this ambition, WGM Engineering provided full redesign, civils, electrical and mechanical installation, and commissioning of the upgrades. A retrofit approach was taken to reduce the cost and time impact on an operational site and increase the lifespan of existing assets. The existing electrical control panel for the plant was modified to carry the capacity required for the upgrade.

The work at Tyndrum was part of a larger six-year investment cycle (SR21), during which WGM has been a delivery partner for Scottish Water.

RSK Group sister company Tarpave worked with WGM Engineering on the finishing stages of the project, laying new tarmac and reinstating the roads closed by the work.

The challenges

Throughout the project’s construction phase, it was important for the plant to remain operational to serve the permanent residents of the village. It was also crucial to complete the work within the specified window, which offered no leeway should any unforeseen events occur.

The age of the plant created such unforeseen hurdles for the team at both a design and a construction level. For sites built before modern mapping technology, like Tyndrum was, it is expected to find unmapped cables and pipes below ground. For this work, this presented a challenge in safe excavation, as the team did not want to mistakenly damage live wires and pipes.

In design, it also presented a challenge. The new screening infrastructure and its supporting cabling and piping needed to be laid a specific distance from these other services and the surface. Finding wiring in places where the designs determined that new wiring should be laid presented a challenge for compliance with these regulations, which prevented their removal or going around, under or over.

The solutions

To ensure the site remained in service throughout the work, temporary screening was installed along with overground pumping to bypass the section under construction. Installation of temporary infrastructure and the upgrades was delivered using vacuum excavators rather than drills and shovels. This approach drew the ground upward to break and remove debris so as not to accidentally strike unknown buried services below the surface.

The presence of unknown services and the need to navigate around these were mitigated by redesign of the upgrades as the project progressed. The draft plans were redrawn three times to ensure all installed infrastructure and service cabling was in full compliance with regulations, keeping it stipulated distances from other pipework and at the correct surface depth.

WGM also worked with surrounding landowners in the area and was able to reuse some of the construction materials to provide hardstanding areas and additional parking for local businesses, leading to an estimated carbon saving of 10–11 tonnes of CO₂ equivalent.

The impact

The work was successfully delivered within the allocated time frame, ensuring no disruption to the village once the summer tourism season began. To further reduce the impact of the plant on visitors, the team installed perimeter fencing to obscure the plant from neighbouring caravan and camp sites.

The completed work has led to improved capability within the treatment plant. It has also contributed to a reduction in maintenance call-outs and cleaning operations caused by spillages. Local businesses and homes have been left with improved facilities, which will help the community cope with the rise in tourism within the area.