Water & Wastewater Treatment

16 | december 2014 | WWT | www.wwtonline.co.uk Thames Water to supply its smaller reservoirs from Speen, but it needed to find an alternative major water source for Cold Ash. The local Water Resource Zone supplying the Newbury area was fully committed and so Thames Water turned to the neighbouring eastern zone serving Reading. Tilehurst Reservoir, 3km west of Reading, was identified as having surplus supplies, triggering the water company's decision to construct transfer mains between the two reservoirs. In January 2011, Thames Water Utilities awarded a £10.2m design and build contract to Optimise – a joint venture consisting of J. Murphy & Sons Ltd, Clancy Docwra Ltd and Barhale plc, plus designers MWH. Construction was not scheduled to start until January 2013 offering the JV an unusually generous year-long design period, which it used well. Thames Water's award was, at the time, a new contract approach setting out only a very broad design brief and allowing Optimise to analyse a wide range of options. We were asked to identify a 'suitable supply source' within the Tilehurst area and design a transfer pipeline between Reading and Newbury catchments routed somewhere within a 15km wide corridor. Much of the landscape between the two reservoirs was rich in local and statutory wildlife sites, ancient woodland, scheduled monuments and even the remnants of an Iron Age fort. Using hydraulic modelling, topographical and environmental surveys, the final route was only marginally longer than the 18.5km minimum length, and succeeded in avoiding the sensitive areas identified. The vast majority of the chosen alignment runs beneath privately owned land, with over 80 per cent classified as agricultural. Tilehurst Reservoir is fed from nearby Fobney WTW through a 710mm medium density polyethylene (MDPE) pipe. This replaced the original parallel 60 year old 21 inch (533mm) cast iron mains, which was capped off but le¡ in situ. The team decided to connect into the live pipe about 1km from the reservoir, and insert its new 355mm pipeline into the original redundant cast iron mains lying alongside it. The team also decided to run the gravity section of the pipeline a further 6km along the route, siting Project focus: Pipes and pipelines

• Cover