SSE - Arborfield Reading
Project details
Client: SSE
Project Start: 01/10/2021
Duration: 4 weeks
Directional Drilling - Installation 200mm and 110mm single bore
DESCRIPTION OF WORKS
Flowtek undertook the Principal Contractor role to install a cable duct to carry a 33KV mains supply beneath the Arborfield Bridge, Shinfield. The installation was required to connect a new, large housing development in the area to the main power grid. Bore holes were dropped along the route where possible to determine ground conditions. A radar scan was also completed to locate any utilities and trial holes were used to prove these targets to provide a safe working route. Flowtek undertook the full design on this project. The ground investigations showed that the conditions in the area comprised largely gravel near surface with London clay laying below this. At the bridge site not only did the installation have to cross beneath one of the bridge foundations but also two water courses. This made any option other than a trenchless solution impossible. It was decided to utilise Horizontal Directional Drilling (HDD) to complete the works. Planning of the crossing showed that the drilled bore would need to pass some 24 m below the bridge foundation, so it was decided to install the cable duct with a 300 mm diameter bore. Once the main bore and reaming operations were completed the team pulled in a bundle of two ducts using a barrel reamer lead. The two ducts comprised both 200 mm and 110 mm SDR11 Black Electric Ducts. The 200 mm diameter duct was installed to carry the main electric cables with the 110 mm diameter duct being used as the comms duct. Both duct pipes were provided as 12 m long sticks. All pipes butt-welded to current water standards and internal/external de-beaded. A butt-fusion machine was utilised to create the pipe strings required each to a length of324 m. A CCTV survey of the completed pipework was undertaken prior to installation to prove all internal beads had been removed. During the course of the installation works, the only problem encountered was flooding in the access field due to heavy rainfall at the end of the completed HDD work. Flowtek had constructed its own site compound and welfare facilities. With this being full design and delivery project, Flowtek had allowed for this area to be matted out so that it did not destroy the field due to construction traffic. This meant that the crew simply had to wait for the water table to go down before removal of all matting and no damage was done to the field. Flowtek also cleared a running ditch that was overgrown for the water to flow as it should.