Water & Wastewater Treatment Magazine
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20 | AUGUST 2016 | WWT | www.wwtonline.co.uk Project focus: Pipes and pipelines at a number of key points, as Stuart Owen, Construction Manager at Dee Valley Water, explains. "We're going to directional drill under the A483 Wrexham bypass and augur bore under the Wrexham to Shrewsbury railway line," said Owen. "We've also got protected trees and hedgerows that we are directional drilling under, and we've got Wat's Dyke and Offa's Dyke, which are protected ancient monuments. We'll need to drill under those too, as we are not allowed to do any excavation work within a 100m exclusion zone around them." "Another challenge, from an ecological point of view, is that North East Wales has the largest Great Crested Newt population in Europe, and we are laying through certain sections of that. So we've taken a three-tiered approach of • Innovations ● Helium testing is being used on the new pipeline when laid, which can zero in on any problems more efficiently than testing with water ● Anchor joints are being used rather than quarried concrete to minimise the carbon footprint of the pipeline's construction ● The project is being delivering using in-house design and build expertise, with local suppliers boosting the economy A map showing the route of the pipeline, which links up the supply areas of Legacy, Llwyn Onn and Boughton Treatment Works already carried out at Llwyn Onn and Boughton, have already reduced the number of discoloured water complaints down from 4.9 per 1000 customers in 2013 to 1.32 in 2015. The further improvements should allow the company to reach 1.01 complaints per 1000, which is the level at which it will be rewarded under its Outcome Delivery Incentive agreed with Ofwat. In terms of resilience, the company says that once the new main is installed it will be able to supply 19% of its total daily demand by transfers if needed, up from 12% previously. The new network will also be able to make maximum use of its impounding reservoirs and will have a reduced requirement for pumping water from the River Dee. On a Totex calculation over 40 years, the company believes it will save £7.5M compared to the alternative if Legacy was still in operation. Summing up the importance of the project, Dee Valley Water CEO Ian Plenderleith said: "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. "This is good news for our customers in the Wrexham area. The first phase of the scheme is the installation of the new main providing a logical and cost-effective solution to a problem which has affected some customers for too long." risk mitigation: we've got red zones which require a large amount of newt fencing and ecological supervision, down to amber and green zones with each tier having less stringent control measures associated with them." At the end of the scheme the company will also be putting in additional newt ponds near Llwyn Onn to fulful environmental requirements against the destruction of habitats, he added. In-house expertise Dee Valley Water is carrying out the design and build using in-house expertise, with an extra five people hired specifically to work on the project and a ten-person team overall. The only aspects that have gone out to external contract have been the specialist directional drilling and excavator hire, while ecological and archaeological consultants have also been engaged. The utility is also embracing innovation by using helium testing on the newly-laid pipes, in a method developed by Suez Environnement. This method, which uses a mixture of helium and compressed air, is an improvement on water testing as it not only tests that the pipes are watertight but also pinpoints the location of any weaknesses which would cause leaks. The work began in May and will run through to December 2017, when Legacy will be decomissioned. To complement the new infrastructure, Dee Valley is carrying out an extensive mains cleaning operation, using the 'ice pigging' method, to rid the pipes of the residual manganese. These measures, in addition to the upgrades