PROJECT OVERVIEW
The Loch Katrine Emergency Spillway Repair was a critical emergency infrastructure project delivered in late 2023 to safeguard one of Scotland’s most important water supply assets. Following severe storm damage, urgent repairs were required to stabilise the spillway at Katrine Dam and protect water supplies serving approximately 1.3 million people across Central Scotland.
EXECUTIVE SUMMARY
In response to storm damage in October 2023 that caused concrete slabs within the spillway to detach, Scottish Water appointed George Leslie Ltd to deliver emergency repair works. Supported by Mott MacDonald, the project was completed within six weeks and successfully restored the dam’s integrity while maintaining operational safety, environmental protection, and continuity of water supply. Innovative temporary works, rapid decision-making, and close collaboration across the supply chain were central to the project’s success.
PROJECT BACKGROUND
Loch Katrine has supplied clean drinking water to Glasgow and surrounding regions since 1859, operating largely under gravity-fed principles with no requirement for pumping. During a severe storm event in mid-October 2023, sections of the spillway apron suffered damage, creating a risk of slab uplift and potential dam failure. Given the dam’s historic status, strategic importance, and supply reach, immediate intervention was essential to mitigate public safety and water-supply risks.
PROJECT TIMELINE
- Mid-October 2023 – Storm event causes spillway damage
- 10 October 2023 – Emergency works commenced
- October–November 2023 – Reservoir drawdown, investigation, design development, and phased repairs
- 24 November 2023 – Works completed and site demobilised
The overall construction period spanned approximately six weeks from mobilisation to completion.
GOALS AND OBJECTIVES
- Rapidly stabilise the damaged spillway and prevent further deterioration
- Protect the security of water supply to Milngavie and Balmore Water Treatment Works
- Maintain the safety of workers, the public, and downstream environments
- Minimise environmental impact during emergency construction
- Deliver repairs compatible with future permanent upgrade works
CHALLENGES OVERCOME
- Live conditions: Works were undertaken while the reservoir continued to spill, demanding careful water management.
- Restricted access: A single-track site access road limited plant size and logistics planning.
- Time pressure: Emergency status required fast-track investigation, design, and delivery, often updated daily.
- Ground conditions: Variable drilling depths and loose upper strata required adaptive solutions, including sleeved drill holes.
- Operational constraints: The Loch Katrine Steamship Workshop remained operational throughout the works, necessitating careful coordination.
ENVIRONMENTAL BENEFITS
- Installation of silt mitigation and slurry containment prevented pollution of the reservoir and downstream watercourses.
- Gravity-fed water supply operations were protected, helping retain the dam’s inherently low-carbon operation.
- Temporary works solutions reduced the need for extensive permanent interventions at this emergency stage.
EFFICIENCY BENEFITS OF THE PROJECT
- Early adoption of interlocking Legato blocks allowed rapid diversion of water away from the working area.
- Design and construction progressed simultaneously, eliminating delays between investigation and delivery.
- Supply chain partners demonstrated flexibility through accelerated and out-of-hours deliveries.
- Lessons learned on drilling methodology delivered time savings during later phases of the works.
COMMERCIAL IMPLICATIONS
The project had an approximate outturn value of £400,000 and mitigated a potentially severe financial risk associated with loss of supply to over one million domestic, industrial, and commercial customers. Successful delivery preserved customer confidence, protected nationally important industrial users, and reduced the likelihood of significantly higher costs linked to major dam failure or prolonged water outages.
CONCLUSION
The Loch Katrine Emergency Spillway Repair stands as a strong example of effective emergency engineering delivery. Through close collaboration between Scottish Water, George Leslie, Mott MacDonald, and the wider supply chain, the project restored the safety and resilience of a nationally significant asset under challenging conditions. The works not only secured vital water supplies but also laid the foundation for future permanent improvements, reinforcing Loch Katrine’s role at the heart of Scotland’s water infrastructure.
