Capital maintenance ... Wales this time
Great fun to have had the opportunity on Tuesday to get to visit the Elan Valley Aqueduct renewal project (I was at Uni with the MD of one of the Joint Venture partners) – riding down the 40m access shaft on a crane hook access cage, then walking several hundred metres along the new 3m dia tunnel to see the Tunnel Boring Machine in action. Amazed that it was costing $100m or so to replace just 5km of the 120km length, and not even to act as an alternative in case of necessary shutdown (which is what I remember being told in my CCWater days), rather it being a replacement for just the three most risk-sensitive sections of the EVA. Anyway, all congratulations to the JV team for delivering such an impressive project and outputs.
Wikipedia explains: "Work on the first 13 miles (21 km) of the route from the Elan Valley was started in June 1896 by Birmingham Corporation Water Department. The aqueduct was built in sections by outside contractors, using three types of construction depending on the nature of the terrain it had to cross. "Cut and cover" was essentially a brick lined channel which was manually dug as a trench, then roofed over and concealed underground. Where the route of the aqueduct encountered high ground above the gradient needed to maintain the downward slope, a certain amount of tunnelling was required, using the same type of channel as above. This totalled around 12 miles (19 km), with the longest single length being just over 4 miles (6.4 km). The third construction type was the use of either bridged aqueducts or inverted syphons to cross valleys and rivers where the ground level dropped too steeply for the required hydraulic gradient to be maintained. The pipeline was continued at the other side of the valley at the same height as the delivery pipe. With the inverted syphon technique, the water naturally fills the lower section of pipe due to the head of water and flow continues downstream. The aqueduct over the River Severn The initial scheme opened in 1906 with two 42 in-diameter (1,100 mm) pipes. Two more pipes of 60 in (1,500 mm) diameter were added between 1919 and 1961(https://en.wikipedia.org/wiki/Elan_aqueduct).
I was fortunate to get to Severn Trent Water's 100 year anniversary celebrations of the opening of the aqueduct at Frankley in 2006, complete with folk dressed up in costume.. And to show the level of 'community interest' there is a fun model of the Elan Valley Reservoirs and Dams in a council park in Birmingham.