George Leslie approached AVK for assistance with developing a solution to operational issues being experienced at Lochgoin Reservoir.
The project originated at concept stage in early 2018, with works commencing on site in 2020. The original design involved modifications to an existing chamber to accommodate an Altitude Valve and Gate Valve. The arrangement was designed to provide controlled compensation flows to the local watercourse, while also allowing water to spill forward from the chamber to Craigendunton Reservoir.
A flowmeter installed downstream of the chamber recorded flows to the watercourse. Under the SEPA CAR Licence, flows were required to be maintained between 9–12 l/s during drought conditions and at 31 l/s during all other times.
The Challenge
During operation, debris from the reservoir periodically blinded the internal filter cartridge within the Altitude Valve. This resulted in misoperation of the valve and, on occasions, overflow events at the chamber.
As the supplier of the Altitude Valve, we assisted with investigating the issue. To overcome the problem, a dual-cartridge filtration system was installed immediately upstream of the Altitude Valve to remove debris from the water before it entered the valve.
The filtration system proved highly effective, with the cartridges typically requiring replacement every three to six months depending on water quality. The cartridges could also be cleaned and reused where necessary. However, George Leslie and Scottish Water subsequently sought a longer-term solution that would minimise ongoing maintenance requirements for Scottish Water Operations. This was also partly influenced by plans to close Amlaird Water Treatment Works, which received water from Lochgoin Reservoir via the overflow arrangement feeding Craigendunton Reservoir.
The Solution
Several options were considered and following discussions with George Leslie and Scottish Water, it was agreed to replace the existing Altitude Valve and Gate Valve arrangement with a single Gate Valve incorporating a gearbox.
This provided Scottish Water Operations with a simple and reliable method of manually controlling the compensation flow as required.
The new equipment was ordered in late 2024 and arrived in the UK in mid-July 2025, with installation works taking place during the week commencing 21 July 2025.
Due to weight restrictions on the reservoir crest road, a PDG Aviation helicopter was used to remove the existing valves and deliver the new Gate Valve to site.
The new arrangement allows Scottish Water Operations personnel to increase or reduce the compensation flow as required, including during drought conditions, while significantly reducing the maintenance requirements associated with the previous Altitude Valve arrangement.
The project was completed following a final site inspection on 1 August 2025, delivering a simplified and robust long-term solution to the operational challenges experienced at Lochgoin Reservoir.
Acknowledgement
AVK/Glenfield Invicta would like to acknowledge George Leslie for their key involvement in this project and for the original case study material.