Boston’s Big Dig

There are good things about America and there are bad things. Here’s a good thing.

In Boston, Massachusetts, the largest inner-city construction project in the world is taking place. The Big Dig, as it is called, is the construction of a spectacular complex of tunnels and bridges to replace the so-called Central Artery. The main highway through the city centre is being buried underground.

Bill Ford Junior, CEO of the company founded by his great-grandfather and well known for his environmental sympathies, recently complained that America has fallen out of love with the automobile. ‘If you remember, in California, people used to write songs about T-Birds and Corvettes. Today, they write regulations’, he lamented (1).

Perhaps inevitably, then, the Big Dig has faced some criticism for its allegedly destructive effect on community. But no Swampy-figure has tried to bury himself in the Dig’s foundations or chained himself to a bulldozer. Overall the USA retains considerable enthusiasm for the automobile as a symbol of personal freedom.

There is also recognition of the technical achievement represented by the Big Dig. In 2000 the US National Academy of Engineering organised a survey of professionals to determine their top 20 engineering achievements of the century. The automobile highway system beat the information superhighway by two places. The citation for the highway system describes many of the developments the Big Dig is taking further:

‘Early in the twentieth century, most of the streets and roads in the USA were made of dirt, brick, and cedar blocks. … The interstate highway system was finally launched in 1956 and has been hailed as one of the greatest engineering public works projects of the century. To build its 44,000-mile web of highways, bridges, and tunnels, hundreds of unique engineering designs and solutions had to be worked out. Consider the many geographic features of the country: mountains, steep grades, wetlands, rivers, deserts, and plains. Variables included the slope of the land, the ability of the pavement to support the load, the intensity of road use, and the nature of the underlying soil.’ (2)

The public tours, the Boston Museum of Science and the Big Dig website (3) illustrate the advances for the interested public.

The construction of tunnels under the old highway, while the traffic flows unimpeded, has required some innovative technology. Sub-zero temperature brine is pumped through pipes to freeze the ground solid. Tunnelling can then take place without disturbing roads, trains, or building foundations, and when this is complete the ground thaws out.

Tunnelling underground while keeping the traffic flowing was impressive enough, but water was one of the project’s main challenges. A variety of underwater tunnels and bridges are being put in place. The Fort Point Channel has been crossed by a tunnel built of concrete sections cast in a specially constructed dry dock, large enough to hold three Titanics. The floating and sinking of the 40,000-ton segments required precision positioning just six feet above an underlying subway tunnel, one of the project’s most difficult feats (4).

With 10 lanes, the Leonard P Zakim Bunker Hill Bridge over the Charles river is the widest cable-stay bridge in the world. The bridge’s towers mirror the nearby Bunker Hill Monument that commemorates the first major battle of the American Revolution. They make a striking addition to the Boston skyline, which looks set to become a local landmark (5).

The old Central Artery carried 75,000 cars per day when it was opened in 1959. Today 190,000 cars per day stretch it to its limits. By 2010 the new Central Artery/Tunnel will carry 245,000 cars per day. The greens like to point out that more roads mean more cars – as if this was a fatal flaw rather than the motivation for the project. However, in this case more cars will also mean more parks. Above ground the old highway will be converted into 27 acres of parkland. The smoother traffic flow will also ease air pollution.

Other incidental benefits of the Big Dig include the fact that gas, electric, telephone, sewer, water and other utility infrastructure has been rationalised, and that archaeologists have had the chance to carry out a number of investigations.

When I returned home to British soil, the contrast was striking. Britain imported the idea of directly elected city mayors from the USA. But London Mayor Ken Livingstone has not shown the flair to create anything like the Big Dig. He has focused on penalising car drivers more than improving transport. His motivation seems to be that we must choose between cars and public transport. But in Boston the subway is cheaper than the London Underground. And it is air-conditioned.

You have to break new ground to make progress, as they say in Boston.

Read on:

Driving London to despair?, by Austin Williams

spiked-proposals: Transport, by Austin Williams

(1) Ford heir says America’s love for the car has lost its zip, New York Times, 8 August 2002

(2) See Highways on the Great Achievements website

(3) See the Big Dig website

(4) See the casting basin section of the Big Dig website

(5) See the charles river bridges section of the Big Dig website