Water & Wastewater Treatment

Valve upgrade brings value to the Elan Valley Case Study A valve upgrade has proved to be the key to keeping a 100-year dam performing its vital role in an area of natural environmental beauty in the Elan Valley. Since 1904, water has been trans- ported from the Elan Valley Reservoirs – created by damming the Elan and Claerwen rivers – to Birmingham. The valley in Powys, Wales, is characterised by diverse flora and fauna and, as a result, the six Victorian dams built across the Elan Estate must be handled with the utmost care and consideration to protect the surrounding environment. Caban Coch, the lowest dam in the sequence, has played a crucial role in carrying clean water 73 miles from Wales to Birmingham for over 100 years. The dam has four discharge lines, 600mm diameter each, and their function is to meet Birmingham's water demands, release compensation flow downstream for the benefit of the environment, enable the dam to drain down quickly in case of emergency, and power a small turbine that generates electricity for the benefit of the local community. In 2016, the discharge capacity was found to be affected due to silt that had built up over the past 15 years in the le"-hand scour line. The problem was further aggravated by ageing valves that were reaching the end of their life, thus Blackhall devised a solution involving 100-year asset life valves to reduce Totex cost and protect the environment around the Caban Coch dam in the Elan Valley reducing the overall degree of control available to dam engineers regarding the discharge capacity. Potential damage to the environment was therefore becoming inevitable, and the problem had to be addressed. Instead of discharging the silt through the unused valves and endangering wildlife downstream, Welsh Water employed a group of divers, who took almost six months to clear the silt. There were several particularly challenging aspects of the process. There was almost zero visibility, and the dive was so deep that a decompression chamber was required on site. Following its clearance, the Blackhall valvologists were called in to inspect the WWT PUMP AND VALVE SUPPLEMENT 2018 13

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