Britain has been arguing about a road tunnel under the Thames since 2009. That is sixteen years of consultations and inquiries, a planning decision that slipped three separate times, and more than \u00a31.2 billion (about $1.6 billion) spent before anyone had consent to dig anything at all.<\/p>\n
The arguing has not stopped. Campaigners wrote to the National Audit Office twice this year about the scheme’s finances, and on July 6 the head of the watchdog wrote back to say he expects to take a look.<\/p>\n
The hardware question got settled anyway. On July 13, National Highways named the company building the tunnel boring machine<\/a> for the Lower Thames Crossing, and at just under 54 feet across it will be the largest one ever put underground in Europe.<\/p>\n It gets built in Germany, shipped over in pieces, and starts cutting near the Port of Tilbury in 2028. What nobody involved will say is what it costs.<\/p>\n The builder is Herrenknecht, the German firm in Schwanau that supplied the borers for the Elizabeth line, HS2, the Silvertown Tunnel and Thames Tideway. Whatever you make of British infrastructure procurement, the manufacturer is not the wild card here.<\/p>\n National Highways puts the cutting face at 16.4 meters, a shade under 54 feet. The machine runs about 394 feet front to back and weighs more than 5,000 metric tons, roughly 5,500 US tons.<\/p>\n Only two machines in history have been built with a bigger face, according to National Highways. The record holder, listed by Guinness World Records, is a 17.63-meter Herrenknecht that cut a subsea road tunnel in Hong Kong. Behind it sits Bertha in Seattle at 17.45 meters.<\/p>\n The European record it takes is also Herrenknecht’s. A 15.87-meter machine drove the Santa Lucia tunnel through the Italian Apennines and broke through in June 2020. The Thames borer beats it by about 21 inches.<\/p>\n It is a variable density design, built for ground that changes on you. Under the Thames that means London clay and chalk with shifting groundwater, down to roughly 200 feet below the riverbed. Fr\u00e9d\u00e9ric Battistoni, Herrenknecht’s head of project management, called it “the largest Variable Density TBM ever.”<\/p>\n Delivery is by sea, in segments, carried up the Thames to the Port of Tilbury and assembled there. National Highways says the machine runs on electricity from renewable sources, part of the project’s pitch to be the first major British scheme that is carbon neutral during construction. Two of the firm’s machines are already grinding under London<\/a> on the HS2 Euston tunnel.<\/p>\n There are two tunnels, each 2.6 miles long. There is one machine.<\/p>\n It launches near the Port of Tilbury in Thurrock, drives the first bore, gets turned around at the far end and drives the second one back. National Highways says the single-machine plan saves money and cuts the project’s carbon footprint, and it does both.<\/p>\n The finished tubes each carry three lanes of 70 mph traffic, more than double the size of the tunnels at Dartford, which has been the only fixed road crossing east of London for more than 60 years. Together they become the longest road tunnel in the UK.<\/p>\n The trade-off is that there is no parallel drive. If the machine stops, the tunnel stops, and large-diameter borers have stopped before.<\/p>\n Bertha is the case the industry always reaches for. Seattle’s machine was bigger at 57 feet, a different type, working different ground, so the comparison only travels so far. It still managed about 1,000 feet of a 9,270-foot drive before overheating in December 2013.<\/p>\n Crews sank a 120-foot rescue pit to lift the front end out. The machine turned again on December 22, 2015, two years late. The tunnel opened in February 2019, 867 days behind schedule, and Washington State won a $57.2 million jury verdict against the contractor that came to about $77 million once interest was added.<\/p>\n Ground that turns out not to match the survey is the exact problem a variable density machine exists to handle. Britain has form in the other direction too. Stella Rose, a 1,775-ton Herrenknecht under the North York Moors<\/a>, holds the world record for the longest tunnel ever driven by a single machine and has been cutting since 2019.<\/p>\n National Highways declined to put a number on the machine. Asked by trade title Highways, the company said the value is “commercially sensitive but is contained within the overall budget for the tunnel contract.”<\/a><\/p>\n The same report noted what comparable kit has gone for. Machines used on the Elizabeth line and HS2 landed between \u00a315 million and \u00a320 million each, roughly $20 million to $27 million.<\/p>\n Set against this scheme, that is a rounding error, which is rather the point. The fight was never about the borer.<\/p>\n National Highways has published a range of \u00a39.2 billion to \u00a310.2 billion, about $12.3 billion to $13.6 billion, depending on which funding model gets picked. Press coverage and campaigners now routinely use a figure of up to \u00a311 billion, about $14.6 billion. Both are in circulation and they are not the same number.<\/p>\n Public money is only one slice. The third Road Investment Strategy, published in March<\/a>, commits \u00a31.65 billion (about $2.2 billion) to the publicly funded works. The rest is supposed to come from private investors, with a consortium taking on construction and long-term operation.<\/p>\n Britain’s trouble with tunnel arithmetic is not confined to the Thames. A two-person consultancy recently argued that a 14-mile tunnel under the Peak District<\/a> could be built for under \u00a32 billion using Norwegian drill-and-blast methods, against a government study that priced the same link at up to \u00a311.6 billion. The gap came down to a single assumption about method.<\/p>\n On July 6, Gareth Davies, the Comptroller and Auditor General who runs the National Audit Office, wrote to the campaign group Transport Action Network<\/a>. “I anticipate that I will examine and report on the Lower Thames Crossing,” he said, adding that his teams are already tracking the programme and that this will inform when any audit work happens.<\/p>\n The office has described the scheme as a programme of significant parliamentary and public interest.<\/p>\nEurope has never run a machine this big<\/h2>\n
One machine digs both tunnels, then turns around<\/h2>\n
Nobody will say what the borer costs<\/h2>\n
The auditors are looking at the money, not the machine<\/h2>\n