Innovative approach impresses Wessex Water

The mammoth task of cleaning and CCTV surveying 26 sewerage siphons in just three months for Wessex Water is currently underway.

The contract, which is worth around £1m, was originally to be divided between three contractors. But, impressed by the approach and methodology put forward by our specialist team, Wessex Water decided to award the whole contract to us.

The project is to assess the structural condition of the siphons using a combination of specialist CCTV equipment and confined space entry teams. The siphons range in depth from 2 metres to 44 metres and pass under major obstructions including the River Avon and its tributaries.

Scheduling of the works is crucial as there are some sites where flows cannot be easily diverted, or are tidal. On many sites significant over pumping operations are required, and in certain instances works are being carried out at night to prevent sewer network levels rising too high during operations.

The team also expects to encounter hard-crusted grease that has built up over numerous years. This is difficult to remove by conventional cleansing methods, and as such we're using specialist high pressure water jetting and suction vehicles to remove the grease.

As part of the approach to minimising the disposal of silt, grease and debris to landfill, we've been closely collaborating with Wessex Water. A grit removal facility has recently been brought online at Wessex Water's Avonmouth Sewage Treatment Works, which segregates and washes grit up to 0.20mm in particle size. This subsequently reduces disposal costs and produces a secondary raw material, which can potentially be recycled.

Gavin Scarr Hall, Managing Director, Utility Services, said: "This impressive sewerage engineering project demonstrates our specialist sewer networks capability.

"Our team has worked closely with Wessex Water to develop an agreed methodology and solutions to tackle the challenges and risks involved on this essential cleansing and survey scheme."