NuGeneration Ltd (NuGen) plans to build a nuclear power station of up to 3.8GW gross capacity at Moorside in West Cumbria. It has commissioned geotechnical studies to gather information on the Moorside site’s characteristics, both onshore and offshore, to inform the detailed design of foundations and ancillary structures and to determine tunnel alignments.
Moorside is one of the largest UK site investigations to be let as a single package – a £20m contract let last year to geotechnical specialist Fugro.
Fugro began work on its £20m contract in December 2015 on the nearshore phase of the Moorside site characterisation. The initial phase of works comprised bathymetry surveys using the vessels Fugro Seeker and the RV Valkyrie.
In early 2016 the Fugro Seeker returned to site to complete the survey and undertake preparatory unexploded ordnance (UXO) clearance surveys for geotechnical borehole locations and seismic refraction lines. In April 2016 the Fugro jack-up barge Aran 250 joined the project for 11 geotechnical boreholes, involving cable percussion boring, rotary drilling and an extensive in situ testing programme.
The vessel Bravo Topaz was mobilised in April and completed a deep seismic reflection survey ahead of schedule. Further work included bathymetric surveys from the Fugro vessel RV Discovery, and shallow seismic reflection and refraction surveys from the Fugro Seeker.
Fugro has also carried out a significant onshore drilling programme for Moorside which has used up to 18 rigs to drill 300 boreholes.
Cable percussive and rotary coring techniques have been predominantly used, as well as wireline drilling, for comprehensive investigations and analysis of ground engineering and hydrogeological data. These include in situ testing of hydrofracture properties, high pressure in situ dilatometer testing, packer testing, and pump testing to determine hydraulic permeability.
Fugro carried out rotary coring to depths up to 220 metres for the extraction of rock samples and large diameter rotary drilling for boreholes.
To reduce spoil, sonic drilling techniques have been used to drill large diameter boreholes for the installation of pumping wells and to facilitate deep geophysical wireline logging. Additionally, some boreholes from the geotechnical programme have been reused to support 2D seismic reflection surveys.
Fugro will present data from the land-based and marine seismic surveys to provide a continuous, land-to-sea profile through the shallow transition zone (intertidal area).
The site team has also dug trial pits to determine viable locations for storing excavated spoil, which will be reused for landscaping. The land-based site characterisation will be supplemented by drilling and groundwater monitoring to support radiological screening undertaken by Amec Foster Wheeler.
Fugro is due to complete the bulk of the site characterisation before the end of the year.