By Lynda Myer
In order to providing additional supply resilience in the west of the capital, the existing inspection shaft on the TWRM that is the vital fresh water artery running beneath London, is due to be upgarded by the Mogden pump out shaft scheme.
Following iauguration, the Mogden pump out shaft will be able to supply the whole of Thames Water’s Hampton area, which covers parts of west London, Kingston-upon-Thames and Twickenham, at close to the normal operating pressure in the event of a failure at the Hampton pump out shaft, whereas the Hampton Water Treatment Works supplies over than 300,000 people.
With capacity of delivering a peak flow of 36Ml/d (417l/s) to give a combined 108Ml/d (1250l/s) from any three of the pumps, four 350kW VSD pumps are going to be installed in the Mogden shaft. They will be capable of being turned down to meet current and future minimum night flows.
Linking a new pipeline to the existing Kew 838mm main to the north of the site, a new surge column, surge tank, additional surge vessels and control panel will be installed on the outgoing connection.
Additionally, for providing extra protection from electrical supply failure, Barhale will install a 2×3.8 MVA HV metered supply power supply, drawing from a network independent of that used by the Hampton pump out shaft.
The location of Mogden inspection shaft is a separate compound of the Mogden Sewage Treatment Works site and containing all new buildings, kiosks and ancillary equipment, the scheme will increase the footprint of the TWRM shaft compound.
A new cover will be installed over the 38m-deep shaft.
According to Barhale water director Shane Gorman: “The design had to overcome several challenges. At 7m the Mogden shaft is a narrower diameter than the 10m typical for a pump out shaft, so our design has had to reflect the reduced available space.”
He also added: “Additionally, this is a clean water solution located within a sewage treatment works site so we have to put in place measures to mitigate and prevent any potential for cross-contamination. We do have the advantage of significant experience of the shaft and the ring main dating back more than 30 years.”
Also the process of inspections and replacement of the white caps along the two sections of the TWRM from the Kempton shaft to the Mogden shaft (6.875km) and from the Mogden shaft to the Kew shaft (4.820km) has recently been compeleted by Barhale.
