Abstract

A 400 kV electricity transmission line is required to cross the Menai Strait to connect the proposed Wylfa Newydd nuclear power station on Ynys Mon (also known as Anglesey) with the mainland. Through an initial feasibility study, the preferred Menai Strait crossing option has been shown to require the construction of a tunnel. This region has a complex geological history, where the oldest strata, consisting of schist and tuff deposits, are interpreted as Precambrian. There are also Carboniferous bedrocks of interbedded limestones, mudstones and sandstones, and Ordovician siltstones and quartzite sandstones. The superficial deposits and landforms are understood to be almost entirely the signature of the last Devensian glaciation, except for occasional deposits and landforms resulting from fluctuations in sea-level. A 3D geological model has been created using published geological records and project-specific surveys, including field surveys, rock exposure mapping, ground investigations and geophysical surveys. This allows the visualization of the anticipated geology of the area, the identification of geological hazards and efficient design and planning for construction.

Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology

Supplementary material: An overview video is available at https://doi.org/10.6084/m9.figshare.c.5045048