History meets innovation on Euston HS2 enabling works

A birdcage scaffold marquee, built by access specialist Palmers, protects the archaeology

The biggest archaeological dig in British history is benefiting from clever engineering and eco-friendly construction plant. CM reports from Euston.

Before the bridges are built, tunnels dug and tracks laid, the largest archaeological programme in Europe will take place along the route of HS2. Over a two-year period, more than 1,000 archaeologists are exploring over 60 sites as part of HS2’s enabling works, revealing over 10,000 years of British history.

The biggest of these is at the site of Euston’s proposed HS2 terminus. St James’s Gardens, off the Hampstead Road, was London’s largest burial ground, where an estimated 61,000 bodies were buried in the 18th and 19th centuries, and it sits almost entirely within the footprint of the station.

Starting in summer 2017, the Costain Skanska joint venture (CSJV), which is managing the £480m HS2 south enabling works contract, has been carrying out a programme of archaeology within the burial ground. As well as uncovering history, the work has been a catalyst for construction innovation, with up to 200 archaeologists and site workers side by side on the 15,000 sq m site. Some 15,128 human remains have been recovered, with 34,622 cu m of material removed as part of the earthworks operation.

CSJV principal archaeologist Caroline Raynor describes the work as “archaeology on an unprecedented scale”. She is based in the site office, where the former National Temperance Hospital was located prior to its demolition, and says her job is “a bridge between engineering and archaeology”.

An example of this is the giant birdcage scaffold marquee that was erected to encapsulate the work – a “cathedral to archaeology”, as Raynor puts it.

The 110m x 90m weatherproof structure, almost as big as Euston station, was designed by temporary works engineer RDG and constructed from system scaffold by access specialist Palmers. The birdcage roof was supported by 15 modular scaffold towers, fitted into foundation bases 6.4m deep, and 300m of spine beams, with spans up to 37m.

“This was assembled without a crane,” says Raynor. “Everything was erected on a working platform and rolled out on the spine beams using a bespoke series of rollers and a winch which pulled the entire tent structure into position. The spine beams run from one end of the marquee to the other.”

This methodology avoided 4,000 hours of manual handling and 9,000 hours of working at height, adds Raynor.

There are sustainable considerations too. The system scaffold is being returned to the market after dismantling of the marquee. The inside of the structure was fitted with LED lighting and charging points were fitted to the scaffold towers for electric plant. “It saved them going off site to recharge their batteries,” says Raynor.

The dig has been constrained by neighbours including Network Rail, houses and hotels, and the Northern Line 23m down. “Excavations have been made to a depth of 6.2m, following drilling of trial holes, which is unusually deep for a burial ground,” Raynor says.

“There is also a weight limit on plant due to the likely presence of voids. White noise showed up during surveys which is probably from crypts in the burial grounds.”

To minimise emissions, CSJV is using seven one-tonne electric ‘ride-on’ mini dumpers, supplied by hirer L Lynch, part of a fleet of eco-friendly machines on the project (see panel).

The 110m x 90m temporary building is almost as big as Euston station

Though the electric plant makes for a healthier working environment, CSJV has had to monitor workers’ blood for lead levels, after finding 286 lead coffins on the site. “About 50% of the 110 archaeologists on the site are female and lead poisoning kicks in earlier for women,” says Raynor.

The archaeological finds provide a glimpse of how local people lived, worked and died in Victorian Britain, with cultural artefacts including fabrics and remains of floral tributes, some still green, inside the mix of lead, tin, iron and copper coffins. Skeletons reflect the medicine of the time, showing signs of rudimentary amputation and dentistry.

The highest-profile discovery was the remains of Captain Matthew Flinders, the Royal Navy explorer who led the first circumnavigation of Australia, who will be reburied in his home village of Donington, Lincolnshire.

“The other human remains will be reburied respectfully at a location to be announced by HS2,” says Raynor.

This main phase of the archaeological works is drawing to a close at Euston, with the marquee dismantled and the earthworks almost complete. However, as the station was partially built over the burial ground, Raynor says more bodies “may be found under platforms 17 and 18 when we start digging in that area”.

“It is unclear what happened to the skeletons in the eastern part of the burial ground during the first expansion of Euston station,” she says. “We’ll be carrying out further archaeological investigations.” 

Meanwhile, archaeological digs will continue on the HS2 route through to the end of 2020. At the Curzon Street station site in Birmingham, 70 archaeologists completed the excavation of another 19th century burial ground last year, unearthing 6,500 skeletons. 

Other planned digs include a Romano-British town in Fleet Marston, Aylesbury, the remains of a medieval manor in Warwickshire, a 1,000-year-old demolished Anglo-Saxon church and burial ground in Buckinghamshire, and a Second World War bombing decoy in Lichfield, Staffordshire.