Page 90

New pipeline will address issues of water quality and resilience

[

A PROJECT TO lay a new 8.5km water main in North Wales, which will bring about significant improvements to the water supply for more than 43,000 people, is around 40% complete. The project is being carried out by Dee Valley Water – one of the country’s smaller supply companies, which supplies the area around Wrexham and Chester – and will link the recently rebuilt Llwyn Onn treatment plant with the network hitherto supplied by the Legacy treatment plant, which will be decommissioned. Risks to supply and quality were identified at the Legacy works, which led to a notice being agreed with the Drinking Water Inspectorate – the company’s regulator with responsibility for drinking water quality – to rebuild the treatment works and subsequently remove the issue of manganese associated with the treatment process at these works, which led to occasional discolouration. A review of the initial plan allowed a better option to be developed. Rather than rebuilding Legacy treatment works, a decision was taken to utilise the high-quality water from Llwyn Onn and to strengthen network connectivity. This new plan will achieve the original outcome but also deliver additional benefits to customers. The construction manager on the project, Stuart Owen, explained: “We looked at the options available to us; looked at the actual project designs and the cost of that project, and we came up with an alternative solution.” In addition to improving the quality of the water by being able to remove manganese, the project will allow measures to improve ‘network resilience’ – the ability for suppliers to co-operate to maintain supply. Said Stuart: “We are currently investigating the option of fetching in water from neighbouring water

90

www.constructionnational.co.uk

companies and vice versa: being able to supply them with water in the event of an emergency.” The CEO of Dee Valley Water, Ian Plenderleith, commented: “We have worked closely with our stakeholders and Customer Challenge Group to ensure that the alternative plan offered a better solution to our customers and we thank them for their support in this process. Overall the plan forms part of our longer term vision of a simpler, high-quality, reliable supply for our local customers.” Local MPs Ian Lucas and Susan Elan Jones, together with local AM Lesley Griffiths, led a sod turning ceremony to mark the commencement of the programme in May. AM Lesley Griffiths said: “Wrexham certainly benefits from having a water company which is locally-based and focused on the community, and Dee Valley Water’s multimillion-pound investment will enable them to offer an even greater service for people in and around Wrexham.” The project has offered a number of challenges. Although the bulk of the pipeline will be 600mm ductile iron pipe laid using open trench methods, there are a number of special sites requiring innovative approaches. The route crosses both Offa’s Dyke and Wat’s Dyke – both scheduled monuments – which will require the pipeline to be laid via directional drilling. This is a complex technology, requiring the expertise of a specialist contractor. There are also a number of Sites of Special Scientific Interest on the route – one of which is home to the largest colony of great crested newts in Europe while another is a protected marshland – and the National Trust’s Erddig Park and House. The next challenge will be to run the pipeline under the railway line that runs from Wrexham to

Shrewsbury. Augur boring to achieve that is due to begin in October. The use of augur boring allows the work to be carried out while the line is in use. A major watchword of the whole project has been the environment – both locally and globally. The great crested newt population is not only being protected by newt fencing, but also encouraged to increase by the installation of ponds. Where the route runs through nesting hedgerows a ‘fingertip search’ is carried out by an ecologist to ensure work does not take place while nests are still occupied. Any hedgerows disturbed will be replaced with similar species. A heritage consultant and eco consultant are involved at all stages and there have been a series of briefings for all staff on the main issues. Globally the carbon footprint of the project is being kept to a minimum by the use of local materials. Where that is not possible the least energy consuming option is chosen – for example the use of anchor joints instead of concrete. Although the joints are imported from France, the reduction in road traffic more than compensated. A notable ‘green’ development is the use of a helium/compressed air mixture to test for leaks rather than traditional water testing. The method is being pioneered on the project as the first in the UK for a new pipeline by SUEZ, the developers of the process. The pipeline is due for completion in December next year, which is the deadline for the taking out of operation of the old Legacy pumping station. In the meantime Dee Valley Water has been carrying out a number of measures to reduce the discolouration. These have included flushing pipes and a new mains cleaning technique called ice pigging. This has substantially reduced the number of discolouration incidents. q

1CHK 2016 mag p1 108 online  

Construction London Build 2016 Scotland Build 2016 Zoos Land of the Lions London Zoo Brexit Working at Height NASC CISRS PASMA CPD MEWPs Roo...

1CHK 2016 mag p1 108 online  

Construction London Build 2016 Scotland Build 2016 Zoos Land of the Lions London Zoo Brexit Working at Height NASC CISRS PASMA CPD MEWPs Roo...