Barhale bags £21m Mogden shaft upgrade

Mogden shaft

Thames Water has selected Barhale for its Mogden pump out shaft scheme.

The project will upgrade the inspection shaft on the ring main to provide additional resilience of supply in the west of the capital.

Once operational, the Mogden pump out shaft will be able to supply the whole of Thames Water’s Hampton area, which includes parts of west London, Kingston-Upon-Thames and Twickenham postcodes, at close to the normal operating pressure in the event of a failure at Hampton pump out shaft. More than 300,000 people take their water from the local network fed by Hampton water treatment works.

Four 350 kW VSD pumps will be installed in the Mogden shaft. Each pump will be capable of delivering a peak flow of 36 million litres a day (or 417 litres per second) to give a combined 108 Ml/d (1250l/s) from any three of the pumps. They will be capable of being ‘turned down’ to meet current and future minimum night flows.

A new pipeline will be connected to the existing Kew 33-inch 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.

Barhale will also install a 2 x 3.8 MVA HV metered supply power supply, drawing from a network independent of that used by Hampton pump out shaft, to provide additional protection from electrical supply failure.

Related Information

The Mogden inspection shaft is in a separate compound in the northwest corner of the Mogden sewage treatment works site. The scheme will increase the footprint of the Thames Water ring main (TWRM) shaft compound to contain all new buildings, kiosks and ancillary equipment.

A new cover will also be installed over the 38-metre deep shaft.

Shane Gorman, Barhale’s water director explained that a number of considerations had to be overcome when shaping the design solution. “At seven metres, the Mogden shaft is a narrower diameter than the 10-metre typical for a pump out shaft,” he said. “So our design has had to reflect the reduced available space.

“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.”

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