The project comprises 1540m of 36-in trunk main (laid circa 1924) which lies in an urban corridor with congested adjacent underground utilities and is situated along the A386 road, residential areas, school grounds, a business park, arable land, and MOD property. Several lining options were considered; however, risks relating to technology application and security of customer water supply had to be considered, as only one other pipeline feeds the water supply zone. Within this area are 47,000 properties, two heavy industrial users, the Devonport dockyard nuclear submarine facility and Interfish (a major food processor). Loss of supply would be disastrous at any time should the only other pipeline into the area fail. Options for cleaning the trunk main and rehabilitation with a fast-cure PU-spray lining were considered even though, at the time of planning, no other pipeline of this size had been successfully attempted. PU lining gave the potential of re-commissioning within the tight timeframe required and also, under extreme conditions, possible re-connection within eight hours, a major advantage over the other lining options such as epoxy resin and slip-lining. Several technical PU-lining breakthroughs were achieved during the project, including optimum mixing and pumping of the Copon Hycote 169 material to ensure a consistent application of 1.5mm thickness on the internal face of the 36-in main. In addition, the in situ lining of bends and tees with a centralizing spray head eliminated the need for their removal prior to lining. Typical lengths of 130m were achieved, requiring the application of some 670li of mixed material at a time. Disruption to residents, motorists, school children and business was minimized and even the school working day remained unaffected, much to the children’s disappointment. The PU lining option developed by T J Brent’s team ensured levels of service were maintained, while still offering a cost-effective engineering solution. Les Metcalfe (South West Water’s regional rehabilitation manager) acknowledged that this had been a remarkable achievement for Brent and South West Water in demonstrating the benefits of using PU to reline the pipe, previously unheard of in the UK. The close partnership between its team and Brent allowed the scheme to be completed on time with no disruption to customers.