Wylfa Gateway Complex


Horizon Nuclear Power Ltd


Wylfa Power Station, Isle of Anglesey



The site is located north east of Tregele Village on the Isle of Anglesey. The site lies to the south of the junction between the A5025 and the access road to Wylfa Nuclear Power Station, and is approximately 4.79Ha in size.

The Wylfa Gateway Complex is to be developed onsite. The complex is to include a new Visitor Centre, a Club House and a District Survey Laboratory/Alternative Emergency Control Centre building with associated infrastructure including road access and car parking. Communal areas are also to be included comprising a multipurpose sports pitch, green amenity space and a large attenuation pond.

Quantum was employed on this contract to carry out a geotechnical and geo-environmental investigation. This will provide sufficient information regarding the ground conditions to enable design of the foundations of the various structures associated with the proposed development, and the geotechnical design of associated infrastructure.

The investigation comprised 25 exploratory hole locations across the site. The locations and number of exploratory holes were determined based upon targeted sampling of the development features and non-targeted sampling on a 50m grid pattern suitable for the development and in accordance with the British Standard BS 10175:2001. The exploratory hole locations comprised the following:

  • 9 windowless sample percussion boreholes to be advanced to a depth of approximately 6m bgl.
  • 16 machine excavated trial pits to a depth of approximately 4.5m bgl.
  • 8 machine excavated soakaway test pits to the required dimensions of the testing.
  • Geotechnical and contaminative laboratory testing.
  • Topographical surveying.
  • Factual report.

In-situ California Bearing Ratio tests were undertaken in 9 of the 16 trial pit locations focused within the areas of proposed hard standing infrastructure including roads and parking areas.

8 soakaway tests were undertaken within 8 soakaway test pits excavated to the dimensions required to undertake the testing.

Standard penetration tests were performed in each windowless sample percussion borehole.

Standpipe piezometers were installed where required to allow for subsequent ground gas and groundwater level monitoring and groundwater sampling.