The gate is used to control water levels in the local area and to prevent flooding of properties downstream, with water levels monitored by ultrasonic sensors indirectly controlling its height setting.
Height is controlled by a hydraulic ram, which incorporates transducers providing precise position signals that are communicated via telemetry to the central control system.
Project manager Richard Patterson says first steps involved measurement of the existing control gate and drawing up designs for the new equipment before moving on to fabrication.
Initial work started with the installation of the stop log system – two sets of barriers, either side of the control gate position – which would also provide some protection for engineers installing the new gate.
As levels rise on the upstream side, the flow would be diverted into a lake, providing storage for the duration of the work.
The original control gate was then removed, using a mobile crane, before final measurements for the sealing rubber strips could be taken, allowing the design of the new control gate to be completed, including filling the internal space with closed-cell expanding foam.
Patterson says installing the new control gate was less straightforward, with installation engineers having to cope with changeable weather and water flows before installation could be finalised.
Two mobile cranes were used – the first, a 100 tonne unit used to lift the new control gate from the transport vehicle to a landing pad; the second, a 55 tonne crane to lift the control gate and lower it into position so that the pivot pins (machined to provide 0.5mm clearance) could be installed.
"This has been quite a challenging project, requiring precision engineering as well as considerable work on site to get the new control gate installed," comments Patterson.
"The complexity of the job has been illustrated by the fact that two crane hire companies declined to carry out the lifting operations due to the remote location and millimetre clearances involved," he continues.
"Once we had found a company prepared to perform the contract lift, we were able to complete the installation and commissioning of the project."