One of the key design requirements of the Saddleworth Community Hydro scheme is to ensure that, once the compensation flow water has passed through the Crossflow turbine, the water must be returned to the natural watercourse.
Prior to the Crossflow turbine being installed, the compensation flow (and its useful energy) was channeled directly to the stilling basin, before re-entering the natural watercourse – in this case Chew Brook. To re-establish this process, a physical link had to be made between the culvert (leading from the turbine house) to the stilling basin. This involved cutting a large hole from the culvert through the outside wall of the stilling basin, through which a pipe was inserted. Water will then pass through the turbine, into the culvert and through the pipe into the stilling basin.
However, in order to make this connection, the first step was to create a water free working area within the stilling basin. This was achieved using an “Aqua Dam”, which was lifted down into the stilling basin using an excavator and placed into position. The working area was then pumped free of water in order to create a water free working environment.
With the working area within the stilling basin reasonably free from water, it was then possible to break through the existing wall by working from both sides. The method for cutting involved the use of wire cutters to minimise damage to operatives and the stilling basin structure that other methods could cause. Once the breakthrough was achieved, a large plastic pipe was then inserted with a gravel bed and surround. With the stilling basin still free from water, the opening around the pipe will be made good. The Aqua Dam can then be removed.
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