The next round of ground and marine investigations for the Forth Replacement Crossing gets underway this week on the north and south side of the crossing and in the Firth of Forth estuary itself.

The marine investigations will provide information about the seabed conditions in the area around the bridge’s proposed North and South towers, which is required to allow Transport Scotland and the future contractor to plan the construction and the equipment required.

Land-based ground investigations are being carried out on land where the connecting roads to the crossing are proposed to be built and also locations on the current road network to establish their condition as they will be retained as part of the connecting road network.

The marine investigations are expected to take up to four weeks to complete, whilst the ground investigations will take place over an eight-week period.

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Paul Mellon, Transport Scotland's geotechnical manager for the Forth Replacement Crossing, said: "Last year we carried out marine investigations to establish the deep ground conditions in the estuary, which involved boring rock up to 90 metres deep in some cases.

"The vast majority of work in this phase is quite different and will involve testing softer alluvial soils to assess the thickness and strength of the seabed sediment up to a distance of around 20 metres."

The majority of the marine investigation work will take place from a vessel in the Forth and will be carried out by Glover Site Investigations Ltd, who carried out the 2008 marine investigations on the project. Work will start in earnest this week following preliminary trials carried out last week.

A small number of boreholes and trial pits will also be dug on the south foreshore near the Port Edgar Barracks sea wall to supplement the findings in that area. This work will be carried out during periods of low tide by BAM Ritchies, the appointed ground investigations contractor for the south side of the Forth.

BAM Ritchies will also carry out ground investigations at various locations associated with the southern connecting roads whilst the same work in the north will be carried out by contractors Norwest Holst Ltd.

These works will include some traffic management on the existing road network to allow tests to be carried out at points on the A90, A8000, M9 Spur and M9.

(GK/JM)