In search of the Age of the Underground 02 Mar 2016

Public awareness of, and support for, underground infrastructure is helping drive the industry out of the specialist fringes of construction and into the mainstream.

Last week’s official visit to London’s Crossrail by Her Majesty the Queen – the 21km east-west line will be known as the Elizabeth Line in her honour when it opens in 2017 – marks a symbolically important moment in the history of the UK underground. Countless bridges and roads in the UK are named after monarchs (the impressive QEII bridge over the Thames at Dartford springs to mind), but for the very first time since Isambard Kingdom Brunel drove his revolutionary shield under the Thames in the nineteenth century a piece of underground infrastructure will be named after a ruling king or queen of England.

The sheer scale of Crossrail with its 42km of running tunnels – as well as its surface visibility, and, indeed, the moderate level of disruption it causes to Londoners as they go about their daily business – have propelled modern-day tunnelling very firmly into the mainstream and created a thirst in the UK for more of the same.

Surveys carried out by Transport for London during three rounds of public consultation ahead of the proposed 34km north-south Crossrail 2 illustrate quite clearly that public support for the principle of underground construction as a solution to the modern city’s infrastructure needs is overwhelming, albeit that inevitable concerns abound in certain locations along the planned route.

Even on mega-projects that have proved less than popular with the public – the planned £50 billion 560km High Speed 2 rail link between London and Birmingham (Phase 1), and London and Manchester and Leeds (Phase 2) springs to mind – it is noticeable that along every step of the tortuous planning and public consultation journey it is tunnels that are regarded as the best mitigation in the battle to win hearts and minds.

In the five years of public consultations since the UK Government first announced details of the 225km-long Phase 1 route between London Euston and Birmingham, an extra 18.6km of TBM bored twin-running tunnels have been added to the alignment.

Among a package of alterations announced by the then UK Transport Minister Justine Greening in January 2012 were included a longer continuous tunnel from the M25 London orbital road all the way north through to the village of Little Missenden in Buckinghamshire. This section would now be a continuous 13.2km twin bore 8.7m diameter tunnel – the so-called Chilterns Tunnel (Fig 1) – instead of two separate tunnels of 9.5km and 1.3km that on the initial alignment were separated by a 2.4km cutting through a designated Area of Outstanding Natural Beauty (AONB) in the Chiltern Hills. This alignment has since been further extended 2.6km northwards to South Heath – making the Chilterns Tunnel now 15.8km long – following the final recommendations of the specially appointed Parliamentary Select Committee that has been investigating over the last two years 1,600 objections to Phase 1 of the scheme.

Meanwhile extra sections of tunnel added in the capital – including two new tunnels of 9km and 4.4km in the London suburbs of Ruislip and Northolt – mean that virtually the entire 22km length of HS2 between the terminus at Euston Station and the Ickenham portal at West Ruislip will be run underground in TBM bored tunnels.

The changes – mostly in response to local public concern about the blight of having a surface-level high speed rail line on their back doorstep – have all but silenced opposition in London, and gone some way towards muting the strongest opposition to the project in the AONB Chilterns section of the route.

However, despite the concessions already made in this critical and environmentally sensitive 30km-long corridor, protestors, with the backing of their Member of Parliament, remain dissatisfied and continue to press for the whole stretch to be run in a single continuous tunnel.

Three possible alternatives for a much longer tunnel through the Chilterns, ranging in length from 24km–29km, were finally dismissed as part of the final directions and recommendations of the Parliamentary Select Committee on the HS2 Phase 1 Hybrid Bill, released on 22 February (2016).

The committee heard that the 24km option would have added £349 million to costs, the 29km option £485 million – although both would have benefited from the removal of two viaducts required in the Wendover area in the original proposal.

A third long tunnel option emerged in 2015 – one that looked to address HS2’s concern that power restrictions in Wendover would make it unfeasible to run a TBM from a north portal situated here. The alternative Tunnel Bored One Way (TBOW) proposal involved staging TBM drives from the southern portal only, a plan that was costed by campaigners at just £42.5 million more than the shorter tunnel excavated from both ends. This low cost estimate was largely derived out of claims that HS2 was guilty of seriously underestimating TBM excavation rates, and applying higher excavation rates to the equation instead. HS2 costed the TBOW proposal at an extra £412 million, based on a single TBM heading leading to project delays.

In the end the committee decided that HS2 was demonstrating “realistic caution” concerning its excavation rates, and that to do so was the “right approach”. The case for the alternative TBOW scheme had not been made, the committee concluded. It has, however, recommended that an extra 2.6km of tunnel alignment be added at the northern end of the Chilterns Tunnel – which means that 60% of this section will now be run underground.

None of this, however, will deter supporters of the Chiltern long tunnel option – who now say they will take their objections to the highest court of appeal in the UK: the House of Lords. Whatever the final outcome, and economic arguments notwithstanding, the protest experience of HS2 seems not so much one of the selfish NIMBY (“Not in my Back Yard!”) of yesteryear; but rather, one of a more altruistic GUMBY (“Go Under My Back Yard!”) nature.

The same levels of support for underground infrastructure are also evident when it comes to plans to widen the A303 – the main road between London and the south-west that comes to a virtual standstill at the first sniff of a holiday season. The road passes the historic site of Stonehenge, and an announcement that this section will be served with a 2.9km-long twin bored tunnel seems to have muted all local objections to the widening plan, including those of that most vocal of defenders of the environment: Friends of the Earth.

In fact, once again, the only bone of contention with the tunnel appears to be that at 2.9km it may be too short. The National Trust – which owns some of the land at the Stonehenge World Heritage site – says it would like to see “the longest tunnel possible”; meanwhile, a local pressure group known as the Stonehenge Alliance goes even further, declaring that at 2.9km the proposed tunnel is “far too short” and should be more like 4.5km.

In Yorkshire, too, in the north of England, a tunnel solution for its planned potash mine has revived the fortunes of Sirius Minerals, which had been trying since 2010 to develop what is projected to be the largest and thickest seam of polyhalite (high grade potash) in the world. Under its original proposals Sirius, perhaps naively, planned to transport the polyhalite to port, nearly 40km away, along a pipeline that would have run through the North York Moors National Park.

In the event it shelved the original plan in favour of plans to construct a 37.5km-long deep level tunnel, using five TBMs operating from four intermediate shafts. This revised design enabled the company – by the narrowest of margins – to win its long-running planning battle for permission with the North York Moors Park Planning Authority. The company, which has attracted tremendous local public support since announcing the tunnel plan, expects to generate annual revenues of up to £2 billion a year and become a major local employer once it reaches full capacity production some time in the next decade. The UK government is even considering assisting with financing the venture in view of the projected economic benefits it will bring to the north of England, and to an area that has been devastated in recent months by the shutdown of the local steel plant in Redcar.

From all of this one thing is clear: tunnels are increasingly becoming a powerful tool in the arsenal of both infrastructure planners and commercial enterprises as they look to balance the social, political, economic and environmental concerns that surround large-scale construction projects. And for a public that is increasingly prepared to pay a premium to mitigate the visual and noise impacts of surface level infrastructure by moving it out of sight and out of earshot, the underground offers an increasingly attractive solution.

This comes at cost, of course, but as technological advancement and innovation open the doors of possibility – and at a declining relative cost, and at a higher level of worker and user safety – the Age of the Underground moves ever closer.