Elan Valley Aqueduct & Birmingham Resilience II
Following last autumn’s visit to the tunnelling part of the Elan Valley Aqueduct rehabilitation, Robert Moyle invited me to visit the company's contract at Severn Trent’s Frankley water treatment works, to the south-west of Birmingham, which receives all the gravity flow water from the Elan Valley dams.
Having been intrigued by the $100m or so that SVT is having to spend on three relatively short lengths of replacement tunnels (15km in total) on the aqueduct from Wales, the visit explained the bigger justification for this phase of the Birmingham Resilience project which is not, immediately, the EVA at all but is designed to deliver new abstraction from the river Severn and transmission to Frankley with a brand new 250MLD additional treatment works at Frankley being built (SVT Drone Team photos attached).
This has been designed to ensure a resilient supply of water to Birmingham a) in case the EVA fails for whatever reason and b) to allow for partial shut downs (’30 days dry possession’) of the aqueduct for rehabilitation and renewal whilst ensuring ongoing supply for the city. It is not designed to be used to meet any additional demand, to my surprise – perhaps due to Environment Agency licensing of abstraction limits).
Robert's company (‘nmcn’) is responsible for design and building of the new works, having been given just two years to meet the end of March 2020 AMP & ODI ('outcome delivery incentives') deadline to spend approx. $150m, SVT having been delayed at the beginning of the AMP period.
Truly impressive how ‘nmcn’ have to thread all these new works and massive pipes in and around an ongoing live works. And the health and safety is exemplary.
To cope with the river water and its turbidity, Veolia are delivering their ‘sand ballasted lamella’ process which uses ‘dense microsand’ to ‘allow the flocs to swell and mature’ ‘counter current lamella clarification’ and a hydrocyclone ‘to separate out the sand to be cleaned and returned into the injection tank to minimise loss’. The clarified water then taken to standard rapid gravity filters, and the sludge to the significant dewatering works also shown in the third photo.