New A557, Widnes—alternative embankment foundations

The new 1·8 km long A557 Widnes eastern bypass (southern section) is the last link in a length of continuous dual carriageway between the M62 motorway and the Runcorn bridge over the River Mersey. The area through which the route passes is flat and has been occupied by industrial development since the middle of the nineteenth century. Most of this new length of road is on embankments up to 8 m high over soft and contaminated ground. This paper is a case history of a project which, in respect of earthworks, was constructed adopting an alternative design proposed by the contractor. By using vibro-replacement stone columns, driven precast concrete piles and an alternative pavement foundation, this avoided the need to excavate, and remove to licensed tips, a large volume of soft and contaminated material. This alternative approach resulted in a reduced cost to the Highways Agency compared with the conforming design and produced a solution with equivalent or better performance. The construction of this alternative was completed several months ahead of programme. Several other alternatives also proposed by the contractor further minimized the environmental impact of the construction works. The paper addresses the development of the alternative scheme from conceptual design through to completion. It examines the ways in which the environmental impact of the project was minimized, and the successful management methods adopted by the contractor to minimize the unforeseen risks. The benefits that can be secured by clients in permitting alternative tenders and a cooperative approach, by all parties, are also be considered.