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Trant has a blast working on pipeline

A new transfer pipeline by water engineering specialist Trant will ensure supply resilience improvements for Wessex Water. Badger setts and unexploded bombs were just some of the challenges that needed to be overcome

A phosphorous bomb was uncovered and made safe during pipelaying excavationsA phosphorous bomb was uncovered and made safe during pipelaying excavations

The project challenges
  • Week-long road closure of the B390 Shrewton Road so the pipeline could be dug across, with temporary closures or diversions of five public footpaths
  • Areas of historic penned livestock grazing areas were avoided at the request of the MoD. Additional ecological obstructions included several badger setts
  • Pipeline was reinforced with ductile iron sleeves and concrete at tank crossings, with the minimum depth of cover increased along the whole route in case of new tank paths
  • The pipeline easement was through MoD land and, due to military restrictions, site staff were required to attend a safety briefing before obtaining permission to work in the controlled areas
  • Unexploded ordnance surveys were completed prior to starting on site. However, some of the located ordnance targets were quite deep and the decision was taken to uncover these during the construction phase when heavier plant would be on site
  • These were found to be bombs, used by the Canadians for practice in WWII. The ordnance was quickly and safely disposed of by the military

Trant Engineering has completed an important contract on part of the water supply grid for Wessex Water. The company was tasked with building 5.7kms of new pipelines in the Salisbury Plain area of Wiltshire.

Wessex Water’s supply grid is being developed to improve the security and reliability of supply to its 1.3 million customers across a 6,000 square mile area covering most of Wiltshire, Dorset and Somerset. Pipelines and pumping stations are being installed to link up existing networks and assets to create a continuous supply grid stretching across the three counties.

Trant’s input into the Shrewton contract included early contractor involvement in the design stages followed by construction of the new pipeline.

Ordnance surveys were carried out over the entire open grassland route as a safety precaution before heavy plant machinery was permitted on site. Some old Second World War ordnance was identified by the surveys on the Ministry of Defence (MoD) land, and Trant immediately liaised with the Royal Engineers team, which quickly made the situation safe. It is believed that the ordnance originated from Canadian forces undertaking dummy runs in preparation for the Normandy Landings in June 1944.

Back-up supplies
The route of the new pipeline is between Chitterne water treatment works (WTW) and a service reservoir at Castle Barn.

It will provide back-up supplies of water to the village of Shrewton, which previously only had a stand-alone borehole source.

Gerry Somers, Trant’s director of contracts, said: “The Shrewton project, which had some interesting challenges because of the terrain’s military usage, was carried out safely and within budget and time and stands testament to our reputation as a specialist in the maintenance of water utility services.”

One of the keys objectives of Wessex Water’s supply grid is to improve the security of supply to customers, even in the event of a catastrophic failure, such as when Severn Trent Water’s water treatment works were flooded in Gloucestershire in July 2007.

That high-profile event caused a civil emergency; more than 140,000 properties were without piped water supplies and 1,400 water bowsers had to be utilised − the most-ever required for an incident in the UK. Piped water was only declared safe to drink just over two weeks later.

Drummond Modley, Wessex Water’s programme manager for the water supply grid, said: “The eight-year, £200M water grid programme is made up of over 40 new projects across Dorset, Somerset and Wiltshire. It has a number of important objectives which will greatly benefit our customers.”

These include:

• Meeting the future water demand for the next 25 years; maintaining supplies even in the event of catastrophic failures of equipment
• Dealing with seasonal or occasional deterioration of raw water quality at some ground water sources due to nitrate concentrations from historic farming practices
• Meeting the planned reductions in abstraction licences at some sources in Wiltshire, as agreed with the Environment Agency
• Ensuring a secure supply of drinking water to our customers and eliminate the standalone nature of several strategic sources in Dorset, Wiltshire and Somerset

Modley added: “Wessex Engineering and Construction Services was pleased with the way that Trant Construction safely built the new pipeline and quickly managed any difficulties that arose during the construction process.”

Asset network
Trant, which employs 700 people and is headquartered in Southampton, was awarded two work-stream contracts by Wessex Water to further improve its regional asset network as part of the utility’s AMP5 framework agreement for 2010 to 2015.

The first involves carrying out civil engineering and mechanical and electrical services (M&E) for the water grid workstream by providing early contractor involvement in the designs process and then the construction and commissioning of new infrastructure, such as the work at Shrewton.

The second sees Trant providing M&E services for Wessex Water’s water and sewage treatment workstream.

For example, the firm recently completed a £9.3M enhancement of a critical sewage pumping station in Bristol.

Wessex Water supplies on average 353Ml of high-quality drinking water to 1.3 million customers every day through a network of 100 water sources, 110 treatment plants, 7,000 miles of water mains and 344 storage reservoirs for treated water.

Topic: Contractors , Pipes & Pipelines
Tags: pipelines , security , drinking water , abstraction

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