Firth of Forth Rail Tunnel Plan Proposed

The Scottish Green Party (SGP) has put forward a proposal to build a rail tunnel crossing below the Firth of Forth in Scotland

The Scottish Green Party (SGP) has put forward a proposal to build a rail tunnel crossing below the Firth of Forth in Scotland, according to a report in New Civil Engineer. The proposal has been welcomed by tunnelling specialists, who believe the tunnel is technically viable, and point to examples of successful deep sea tunnel engineering projects in Norway and Japan.

The proposal is part of the Rail for All plan, which was published by the SGP on 12 January 2021. Its aim is to modernise the rail network with a £22bn revolution, which will be carbon-neutral and affordable to all. The tunnel plan is aimed at reducing congestion around the Haymarket Station in Edinburgh, and pressure on the Forth Bridge.

A tunnelling specialist, who declined to be named in the report, commented: “Long tunnelled sea crossings both by Immersed Tube and bored tunnels are feasible. The bored tunnel proposed would pass through Carboniferous rocks, some of which have been mined for coal, which would pose a challenge.”

The SGP estimates the cost of the tunnel will be around £4bn to £6bn, and if it were to go ahead, the project would take five to seven years, using modern bored tunnelling techniques. The proposed twin bore tunnel would be 14.5km long, driven under the Firth of Forth from Abbeyhill to Seafield, and connecting to rail stations at Leith and Kirkcaldy.

Challenges for the project are likely to be from environmental concerns around contamination and land use, which may draw legal objections. The integration of the new line with existing networks is also expected to present technical issues. If it were to go ahead, it would substantially reduce journey times around the east of Scotland.

LBA Chair Martin Knights reveals that research and assessment carried out in the mid-2000’s for the new Forth road bridge also examined the possibility of a tunnel. The results of this survey have convinced him that the deep-sea tunnel is technically viable.

He comments: “While not without hydrographical and geological risks from carboniferous and volcanic formations, dykes, faults and varying profile of sea bed and rockhead, recent subaqueous tunnelling projects in the UK and Nordic Countries have demonstrated that tunnelling of this nature is entirely feasible.”

He continues: “This is demonstrated by the spectacular advances in tunnel boring machine and blasting technology for hard rock and variable ground conditions.

“These advances in tunnelling technology make it possible to consider undersea transit crossings such as the UK government`s current Union Connectivity initiative, chaired by Sir Peter Hendy, between Northern Ireland and Scotland.”

According to the report, the Scottish Government has not ruled out the proposal, but stressed the need for further scrutiny. This is likely to be concerned with further assessment of the feasibility, risks, cost, and delivery of the project.

A Strategic Transport Projects Review, setting out major projects for the next 20 years, is expected to be published by the Scottish Government next month.

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