Elan Aqueduct
Carried water from the Elan Valley Reservoirs to Birmingham
c.1904 The aqueduct is 73.5 miles long; it has a total fall of 169ft. Almost exactly one-half is either tunnel or cut-and-cover construction, with a capacity of 75,000,000 gallons daily. The remainder consists of inverted siphons laid across the larger valleys, comprising three pipelines, two of cast iron pipes 42in diameter and one of concrete-lined steel pipes, 60in external diameter.
1949 work began on laying a further 60in diameter main to increase the capacity of the siphon sections to that of the remainder of the aqueduct.
There are eleven siphons across the larger valleys, that across the Severn Valley being 17.5 miles long, five river crossings by bridge, of which the one across the Severn is 624ft long and one railway crossing.
Not included in the original scheme were thirty roughening filters, covering an area of 2.75 acres, composed of coarse sand in layers of graded gravel installed to prevent the deposit of finely divided peat in the aqueduct. These are at the lower end of the short inflow tunnel from the Caban reservoir. After filtration, lime is added to the water. Two powerhouses at the foot of Caban Coch generate power by turbines driven by the compensation water with two 160kV A turbo-generating sets. Surplus power was sold to the South Wales Electricity Board.
Not sure what this image is:
Near Wolverley on the Staffordshire-Worcestershire Canal.
Perhaps this is the site of a crossing of the canal by a siphon on the aqueduct.