South Bridgwater to Biddisham
Client: National GridProject Management: Balfour Beatty
Description: Groundworks contract for the southern overhead section of the Hinkley Point Connection Project - a high-voltage electricity connection between Bridgwater and Seabank, near Avonmouth.
Duration: 2 years
The connection is 57kms long and comprises 48.5km of overhead lines using the world’s first operational T-pylons. The remaining 8.5km of cable runs underground through the Mendip Hills Area of Outstanding Natural Beauty, leaving it free of pylons for the first time since the 1960’s. Upon completion it will provide new sources of low-carbon energy for homes and businesses in the South West. Work on the southern section entailed the installation of circa 12km of temporary haul roads and the construction of 45 work areas (a combined piling mat and crane platform area) across the Somerset levels ready for the erection of the pylons. The unique nature of the low-lying levels meant that the work included building a network of ditches, damning off and reaming multiple water courses and constructing culverts to divert water under the haul roads. Each watercourse required a bespoke solution and required careful planning to ensure all measures were reversible at the end of the project.
KSG partnered with Soil Science to minimise the aggregate requirement for the haul roads and work areas. The original design required the stripping of the topsoil and laying geogrid and 6F5 aggregate. Soil Science developed the SUREGROUND™ reversible soil enhancement system which mixes in-situ site soils with a proprietary binder to stabilise the soil and increase the load bearing capacity of the ground. By embracing this technology, it was possible to reduce the size of soil storage areas and eliminate the requirement for large quantities of primary aggregates; reducing lorry movements and reducing vehicle related emissions. This helped to reduce installation time and ensured community relations were preserved thanks to fewer vehicle movements on the local roads and associated noise, dust and vibration levels. Ultimately, 50% of the whole scheme was completed with the SUREGROUND™ temporary stabilisation solution which is fully reversible.
On completion of the southern section KSG removed the haul roads and reinstated the Somerset levels. Aggregate was recycled and repurposed for use on another nearby development site, reducing the carbon footprint of the project significantly.