Lewes' pipe-jack and shaft sinking success

摘要

Weaving a 1.15km long 1.2m diameter tunnel under the streets of south east England's famous beauty spot, Lewes, was always going to be a challenge. Editor, Tris Thomas visited the site and describes how this, and the sinking of six large shafts was achieved six months ahead of schedule. Although small compared to many of today's tunnelling projects, technically speaking, Southern Water's (SW) recently completed US$26.3M Lewes CSO (combined sewer overflow) scheme in South-east England has crammed a lot of engineering into a tight and environmentally sensitive space - in a very short time. The project is a major slice of SW's K3 5-year spending plan and has been designed to prevent previous overflows of Lewes' 20 antiquated CSOs into the River Ouse and other local drinking supply watercourses during periods of heavy rain. To do this, as mandated by the UK's Environment Agency (EA), a myriad of underground construction techniques have been used to weave the new overflow storage scheme under the town's tight streets, including a 1.15km long, 1200mm i.d. pipe jacked storage tunnel with a 1.95M litres storage capacity, 580m of 450mm directionally drilled pipeline, 75m of 225mm diameter and 40m of 450mm diameter auger bored connections, and open trenching.