The eight year programme of work includes the construction of more than 200km of new pipelines, 24 major new or refurbished pumping stations and 12 new storage tanks ranging in capacity from 2 to 8 million litres. For the new pipelines there are more than 120 crossings required that include major trunk roads, major rivers and main railway lines.
With thrust blocks presenting transportation and installation challenges and raising environmental concerns, Saint-Gobain PAM's Universal joint offers the alternative of a high performance self-anchorage system, which securely moors a pipeline while saving many tonnes of concrete.
The Wessex Water project on which the Universal joint is currently being used is the Corfe Mullen to Salisbury trunk main that is part of the water supply grid scheme - the largest ever undertaken by Wessex Water. The eight year £225 million programme of works spans two AMP periods and comprises more than 50 individual projects designed to resolve resilience issues within the water supply network. It will improve inter-connectivity within the existing water supply system to enable water to be moved from areas of surplus to areas of need and hence improve resilience to drought and unforeseen events.
Saint-Gobain PAM UK began supplying its EN545 approved natural ductile iron pipe range last year for the project. By its completion in 2018, the scheme will see some 120km of pipe supplied by the company in a range of diameters from 700mm down to 350mm.
The project falls into the category of a ‘resilience scheme’, which means that once it is completed, it will be able to accommodate both high and low water demand levels. The Universal joint is ideal for such schemes since it can handle working pressures of up to 64bar (depending on diameters).
Saint-Gobain PAM began supply of its ductile iron pipe range at a time when floods hit the project’s location. Nevertheless, transportation of pipework and delivery to site were successfully achieved, despite the challenges of a landslip and road closure. In addition, the company was required to accommodate preferred rural supply routes. Saint-Gobain PAM UK’s sales director, Simon Cottingham takes up the story:
“We are working closely with the Wessex Water team to create value and ensure a highly competitive total installed cost. The project is another great example of where ductile iron pipe wins out when compared to other materials
with increased total installed costs due to the requirement to import a granular bed and surround to structurally support their pipe.
“Ductile iron pipes offer installation flexibility, with multiple pipes in a single trench, as well as a relatively short and discreet installation footprint, meaning trenches do not need to be left open for extended periods. With the native soils for this scheme being primarily chalk, the ability to backfill trenches quickly is key, since chalk left at a trench side for long periods could be exposed to the effects of heavy rain, making it unsuitable as a reinstatement material.”
When completed the water supply grid will allow Wessex Water to meet future demand for water and improve the security of supply for customers. The scheme will meet reductions in abstraction licences required by the Environment Agency to improve flows in some rivers and protect their ecology. It will also mean that seasonal or occasional deteriorating raw water quality will be accommodated.