THE PROJECT

GEL were employed to undertake a ground investigation to provide data to assist with the design of equipment foundations for Swansea Greener Grid Park project; specifically involving alterations to an existing, large substation.

The projects aim was to help achieve zero carbon emissions in Wales by increasing the stability of the electricity grid and the amount of renewable energy being delivered to the grid network by the installation of large electrical machines with flywheels (called synchronous compensators) that replace the spinning turbines of a traditional power station but without emissions of carbon dioxide.

This required not only the installation of new equipment on the site, but also provision of new cable routes to link the facility to the network.

THE CHALLENGE

Access to the site was gained via a narrow lane which serviced a number of private properties and included a weight restricted bridge. Careful consideration of traffic movements and deliveries of plant and equipment along this lane was necessary to minimise any disruption.

The site was located predominantly in agricultural land adjacent to the main substation and access to the majority of investigation locations required passing over significant distances of soft ground, hindering access of plant and materials. The distances from access points to investigation locations meant that use of access trackway was impractical.

In order to obtain information to construct the foundations, access routes and cable runs, numerous different investigation techniques were employed, each appropriate to the end use of that particular part of the site.  This required close collaboration between our own plant and engineers, together with that of specialist sub-contractors, land owners and the Client in order to complete the investigation efficiently and effectively.

THE SOLUTION

Prior to any intrusive works, it was necessary to undertake  utility avoidance surveys of each location to ensure that they were clear of any buried services. Our team of utility surveyors ensured that any excavations could commence with confidence that no buried services were present.

In order to be able to move equipment to the investigation locations effectively and without the significant cost and inconvenience of installing trackway, GEL mobilised tracked ‘mules’. These are more commonly utilised alongside our slope climbing drilling rigs but are able to easily traverse  variations in topography and ground conditions in order to service investigations with equipment and materials.

The investigation utilised a variety of techniques  to obtain high quality data which included dynamic sampling and rotary coring rigs, dynamic probing (DPSH), machine excavated trial pits, and Electrical Resistivity Tomography (ERT) surveys.

Access along the lane to the site was managed by co-ordinating deliveries of plant, equipment and materials to minimise disruption and by ensuring all staff were aware of the issues from daily site briefings and signage placed along the lane. Plant deliveries were transferred from large lorries to smaller vehicles at a point prior to the narrow lane to be able to gain access to the site.

Close co-ordination between various site activities was required to enable the varied investigation techniques to work simultaneously, thereby managing the site time efficiently and effectively.