Written evidence submitted by COWI (CISFL0010)

Introduction to COWI

COWI is an international engineering consultancy specialising in transport infrastructure, renewable energy, and ports and marine. Our experience means we are uniquely positioned to drive forward transformational infrastructure and green energy solutions.

By drawing on our involvement in pioneering projects worldwide, such as the Toronto and Copenhagen Metros, Iceland’s Hellisheidi Geothermal Energy Plant and New York’s Empire Wind Farm, this allows us to inform and design projects in the UK, such as the Battersea District Heating System, the Mersey Gateway Bridge, Silvertown Tunnel, the Lower Thames Crossing and the Thames Tideway Tunnel.

In Scotland, we are involved in a range of critical infrastructure projects including Coire Glas Pumped Storage, Thistle Wind Partners offshore windfarm and, pertinent to this inquiry, Shetland Islands Council’s (SIC) study into inter-island tunnels.

Our strong presence across Iceland and Greenland gives us a nuanced understanding of North Atlantic infrastructure priorities and the critical pathways driving the green transition.

Infrastructure alone cannot solve every challenge. However, by working collaboratively with government, local government, stakeholders and industry, we believe that there is an opportunity to bring forward resilient, large-scale sustainable solutions to address the climate crisis, unlock economic growth and address the pressing infrastructure needs of our country.

COWI & Shetland Islands Tunnels

COWI has a long association with Shetland and with the delivery of major infrastructure in island and coastal environments. For more than two decades, our engineers and technical specialists have supported marine, energy and transport projects in the Northern Isles, building a detailed understanding of Shetland’s geography, economy and community needs.

COWI’s roots are in Scandinavia, where fixed-link infrastructure between remote islands has been developed for more than half a century. COWI has supported a range of Nordic subsea and rock-tunnelling projects, and our work is informed by lessons from the Faroe Islands’ long-established fixed-link programme, where permanent tunnel connections have provided an alternative to ferry services and supported the long-term sustainability of small island populations and dispersed communities.

This experience has shaped a body of practical knowledge around how fixed links can serve remote geographies, broaden access to services, and maintain continuity of movement across island groups.

In Scotland, COWI is currently involved in underground and rock-tunnelling works at the Coire Glas pumped-storage hydro project, providing direct experience of drill-and-blast techniques within Scottish geology. This reinforces the wider Nordic evidence base that rock tunnelling to island communities is technically straightforward where geological conditions are suitable.

Taken together, our history in Shetland, experience in the Faroe Islands and Nordic region, and practical rock-tunnelling capability in Scotland provide a relevant and transferable foundation for supporting SIC’s exploration of fixed links.

We are working with SIC and its partners to assess contracting, financing and delivery approaches in a structured way, consistent with business-case requirements and wider public-sector accountability.

COWI is leading the development of the Fixed Link Model as part of this study. This work will: 

●       Seek to define what SIC has to do to transform itself into a delivery organisation

●       Develop a single tunnel option to a scheme design stage

●       Undertake soft market testing with internationally experienced contractors:

○       to test program and construction costings developed

○       establish the appetite for international contractors to come to Shetland to build tunnels

●       Finally, it will explore routes to funding to pay for the investment and its maintenance

Q1

Many parts of remote and rural Scotland, particularly on the islands, are economically and demographically fragile. Depopulation is not a new phenomenon, however, it is now severe enough to place the sustainability of some island communities at considerable risk. 

Nonetheless, there is reason to believe that the economic future for these islands could be positive as a result of the opportunities in industries such as renewables, aquaculture, tourism and space.

However, as our global experience tells us, people will be attracted to live in remote and rural places if they are easy to get to, easy to get around, digitally connected and with job opportunities and an affordable standard of living.

This is increasingly not the case in Scotland’s islands, which are largely served by ferries and experiencing increasing levels of disruption due to the prevalence of climate change-related weather events, combined with numerous breakdowns in the ageing ferry fleet. In most cases, there is no alternative mode of transport. The ferries are truly a lifeline.

The situation in Scotland is similar to what we have seen in many other parts of the world, with a particularly strong resemblance to Scandinavia and the Faroe Islands. 

However, whilst there has been direction from central government in these countries aimed at sustaining and regenerating remote communities - such direction has not existed here.

Local authorities and the people they serve have the ambition, but lack the resources to execute a multi-million-pound infrastructure project. Backing from central Government is essential, along with creative finance options.

Q1.1

The most obvious cases for fixed-link connectivity are in the Northern Isles and Western Isles. There is a deep reservoir of social, climate and economic opportunities which can come about as a result of fixed links.

First and foremost, fixed links revolutionise the way that people can move around in their everyday lives. Simply going to work, to school, to a medical appointment, to visit family or to travel to mainland Scotland would be completely reimagined by a fixed link. 

The arguments in favour of tunnelling in Scotland’s islands are similar to the arguments for the 25.4-kilometre Rogfast tunnel in Norway, in which we are involved. On completion, the tunnel will be the longest and deepest subsea road tunnel ever built.

This project will: 

●        Reduce journey times by 35 minutes 

●        Facilitate an expansion in the housing and labour markets 

Tunnelling between Scotland’s island hubs and their smaller, remote islands is not particularly challenging from a technical perspective. The tunnels currently being proposed are all relatively short compared to some of the projects we work on around the world. 

Furthermore, because Scotland sits predominantly on rock, we can use the ‘drill and blast’ technique, successful all over the world in the creation of subways, canals, and roads to hydroelectric schemes, which is similar to the one COWI is working on right now at Coire Glas pumped hydro storage in the Highlands. 

There is demand for fixed links in various islands, and we are aware of the Scottish Government’s intention to consider tunnels to complete the north-south connection of the Western Isles. However, the islands where tunnel proposals and work are most advanced are in Shetland, under the leadership of SIC.

The reason for undertaking fixed link modelling for SIC is to establish the deliverability of tunnels in Shetland. This does not concern itself with the technical or engineering feasibility of constructing such infrastructure, but rather on the mechanisms of procurement, organisational structure and financing to deliver the link.

This is the most detailed work ever undertaken on tunnels in Scotland, and will not just inform Shetland’s tunnelling options but those of island communities across the country.

We are clear that from an engineering perspective creating fixed tunnel links between our islands and Scotland is technically feasible and we have the civil and mechanical engineering skills, and experience, to design and construct the tunnels.

In relation to design standards and codes, very little would need to be changed from those currently used in the UK, but lessons would be taken from recent developments in Norway, which are straightforward.

We firmly believe that the conversation around fixed links should not get stuck on engineering feasibility, but concentrate on whether, as a society, we wish to increase connectivity and, if so, how we fund the links.

Q1.2

We have not experienced any significant disadvantages associated with fixed-link infrastructure in our projects worldwide. In practice these connections are consistently well used, positively received by communities and transformative of everyday life. 

The Faroe Islands are a clear example. Initial concerns that fixed links might undermine rural or island communities have not materialised - the tunnel network has strengthened them. Improved connectivity has made housing more accessible, encouraging young people to return from abroad and enabling them to live outside the capital. There is also clear evidence of repopulation in some of the most remote islands.

Q2

Our global experience in creating fixed links gives us a high level of confidence that tunnelling projects in Scotland’s island communities would:

●        Provide significantly more resilient transport links

●        Underpin regional and national economic growth 

●        Sustain key sectors, such as whisky, aquaculture and renewables, and create jobs 

●        Help to reconfigure public service provision

●        Increase the provision of affordable housing

●        Reduce depopulation

Some examples from elsewhere include:

Fehmarnbelt Fixed Link, Denmark: 

The 18-kilometre Fehmarnbelt Fixed Link connecting Denmark and Germany will be the world’s longest combined road and rail-immersed tunnel. COWI acts as the primary consultant for FLC (the contractor to the owner and operator of Sund & Bælt).

As one of hundreds of projects within the trans-European transport network (TEN-T), this transport corridor will help improve mobility, cohesion and interoperability within the European Union, resulting in an overall reduction in carbon emissions. 

Gothenburg West Link (Västlänken), Sweden: 

The West Link is set to be an eight-kilometre double-track railway with a six-kilometre railway tunnel and three new stations underneath the city of Gothenburg. COWI is involved in multiple parts of the project.

The new railway not only makes local and regional public transportation more accessible and quicker but also contributes to West Sweden becoming a larger labour market region by improving connections between Gothenburg and other locations. 

Q2.1

Evidence from Scandinavia and the Faroe Islands suggests that central government must be fully supportive of a programme of fixed links; indeed, in most cases they are the strategic drivers. 

It is clear, through our work with SIC, that the authority is highly competent, but the financial requirements of tunnelling are far outwith the size of the local authority. This means the Council will have to leverage finance either from the Scottish Government, the UK Government, private lenders, or a combination of these. 

Central government should be taking a keen interest in fixed link infrastructure, both because of the role it can play in the social regeneration of its remote and rural areas, but also because of the economic advantages it can unlock in the development of renewable energy and the growth of key industries such as Scotch whisky, aquaculture and space. We are seeing investment in such infrastructure being accelerated in parts of the world due to the geopolitical situation.

Q3

COWI has deep experience in tunnelling throughout the world, including in territories similar to those that we would experience in Shetland and other Scottish islands.

The tunnels we are working on in Shetland, including the ‘test case’ tunnel between Mainland Shetland and Yell, are relatively short, as are other tunnels which have been proposed in the Western Isles.

A selection of our current tunnelling work includes the following. It should be noted that examples provided throughout this submission, Coire Glas, Gothenburg and 2nd Avenue are all rock projects, similar to Shetland.

●        The Lower Thames Crossing is going to be the longest road tunnel in the United Kingdom, running for four kilometres under the River Thames east of Gravesend and Tilbury. It will consist of two bored tunnels, each 16 metres in diameter, one for southbound traffic and one for northbound traffic. When complete, it will be the largest-diameter bored tunnel in Europe. 

The new crossing will ease congestion on the existing Dartford Crossing, which handles around 55 million trips every year. It will also provide more than 70% additional road capacity across the river, unlock major investments and create new jobs while minimising construction impacts on the riverside marshes and riverbed. COWI is the technical partner on the project in a joint venture with Arcadis and Jacobs.

One of COWI’s key responsibilities is the development of the preliminary design for the bored tunnel, delivering optimum solutions for tunnel safety, availability and customer experience.

●        The 25.4-kilometre Rogfast Tunnel in Norway will consist of two dual-lane tunnels under the Boknafjord, north of Stavanger. On completion, the tunnel will be the longest and deepest subsea road tunnel ever built.

The ambitious project will shave 35 minutes off the journey on one of Norway's busiest roads between Stavanger and Bergen, while facilitating an expansion in the housing and labour markets in the region. The two tubes of the main tunnel will be connected by cross passages for emergency and cross tunnels for diversion of traffic when necessary. Additionally, four caverns are planned for each tube to break the monotony passengers may feel driving through a tunnel of this length.

COWI prepared the conceptual design as a basis for municipal plans, had overall responsibility for the tunnel design and construction, including geological assessment, tunnel installations, operational safety and roads in tunnels, visualisation and video presentation. The tunnel is planned to open in 2033.

●        COWI has been appointed lead designer for the 2nd Avenue Subway Expansion, New York, one of the largest ongoing transit infrastructure programs in the United States.

The initiative will create a modern, efficient and attractive transit system for New York City, with the primary objectives of improving access along Manhattan’s East Side, particularly within the East Harlem community, reducing congestion on the heavily used 4-5-6 Lexington Avenue line and enhancing mobility for residents, commuters and visitors throughout the city.

This is a long-awaited transportation investment for the residents and businesses of East Harlem. It will reintroduce rapid transit to the neighbourhood after more than 80 years, add three new ADA-accessible stations at 106th, 116th and 125th Streets, improve daily mobility for more than 100,000 riders and substantially reduce crowding on the current Lexington Avenue subway line.

●       COWI is involved in the delivery of Coire Glas, pumped-storage hydroelectric, in the Highlands.

The engineering design encompasses extensive underground and civil-engineering works: the plan includes a dam to create the upper reservoir, plus around 17 km of tunnels, including headrace and tailrace tunnels up to 10 metres in diameter, leading through the mountains.

COWI, working alongside Stantec and other partners (including the contractor STRABAG), developed bespoke designs for the exploratory audit and supervised the ground investigation programme that supports the design of the full scheme.

Once operational, the project will help to bridge the energy gap at transmission level and store excess energy during peak periods.

●       COWI was involved in the Silvertown Tunnel, a twin-bore road tunnel beneath the River Thames, connecting Silvertown on the north bank with the Greenwich Peninsula on the south. The tunnel spans approximately 1.4 km (about 0.9 miles).

Each bore carries two traffic lanes, with one lane in each tunnel reserved for buses and heavy goods vehicles, and the other lane available to general traffic. The twin-tube design includes eight cross-passages between the tunnels to provide safety, ventilation, maintenance access, and emergency escape routes.

The Silvertown Tunnel represents a major civil-engineering achievement: a modern underwater bored-tunnel crossing under a heavily trafficked river, built with attention to structural integrity, safety, environmental mitigation (via barge transport of spoil), and efficient use of resources.

The successful delivery of this project demonstrates how contemporary tunnelling methods, combining TBMs, precast lining, and innovative reuse of equipment, can deliver urban infrastructure that meets high demands of capacity, resilience and safety.

The most important lesson we can draw from these projects, in relation to our current ongoing work in Shetland, is that tunnelling in Scotland’s islands is relatively straightforward from an engineering and construction perspective.

The distances involved are significantly shorter than in some of our global projects (our ‘test case’ tunnel over the Yell Sound is the longest of the potential links, at 6.5km, compared to the Rogfast Tunnel, which is around four times longer).

Furthermore, the tunnels themselves are likely to be relatively simple with a small diameter (single-carriageway, single tunnels, compared to, for instance, the eight-lane Fraser River Tunnel).

Indeed, the inspiration for the studies being carried out in Shetland are the socio-economic results demonstrated in the Faroe Islands through its programme of connecting islands by sub-sea tunnels.

The Faroe Islands population are in the top 10 global economies with respect to income per capita, they have seen a 10% increase in population over the last decade and are demographically, socially and economically stronger than other small island archipelagos.

They put this down to 75 years of investment in infrastructure including the construction of inter-island tunnels. This is driven by a political leadership and a consensus around a ‘Vision’ of One Island City where everyone is connected to the capital in one hour’s drive. [1]

Q3.1

The Faroe Islands have historically relied on ferries for inter-island travel. Its rugged geography and dispersed population posed significant barriers to mobility and economic integration. Over time, strategic investments in tunnels and bridges have transformed accessibility, supporting economic growth and social cohesion.

There is significant evidence of its impact in a document prepared by Landsverk, which we recommend to the Committee - Removing the Island Barrier: Socio-economic impacts of tunnels (2022).

It concluded that there was strong evidence that building a tunnel: 

●        Arrested population decline or encouraged repopulation of the remote island

●        Reduced the average age on the remote island

●        Increased the average income per capita on the remote island

Tunnels have reversed population decline in connected regions, lowered average age, and increased income per capita. Improved connectivity fosters integrated labour markets, housing development, and resilience against weather disruptions, strengthening overall economic productivity.[2]

While the Faroese have long been content about the positive impact on demographics, jobs and wealth, the element which required external help was finance.

As a result, all subsea tunnels in the Faroe Islands have been built through a Public Private Partnership (PPP) model, owned by the government. More recent tunnels have sought investment through global capital markets.

The challenge lies not in engineering or construction capability, but in political vision and ambition, supported by sustainable financing and decisive central government backing.

December 2025