Repair works on an ancient monument in Wiltshire (England) have been temporarily halted because of the recent heavy rain. Engineers and archaeologists have been working to stabilise Silbury Hill, believed to be the world's largest man-made prehistoric mound. But English Heritage has now stopped works because of complications caused by instability above the central chamber within the centre of the Hill. These problems have been exacerbated by recent heavy rain.
     The engineering contractors Skanska, who were carrying out structural repairs for English Heritage, pulled its miners off the hill, fearing that the 40-year-old tunnel in which they were working might collapse. A few days ago their temporary access track was under a metre of water. "We cannot go back in until the weather improves, but we fear there have been further collapses within the voids left by earlier archaeological investigations," project director Rob Harding said. "Ironically, I consulted local rainfall records in planning this work, to choose the driest part of the year, but we have really had a huge amount of rain, and we believe it has caused further damage." At best, work originally planned to finish within weeks has been delayed by months. At worst, the stability of the whole structure has been weakened.
     In floods five years ago, a chasm opened at the top of the hill, where a poorly filled 200-year-old shaft collapsed, and water poured down into the structure, seeping into voids left by generations of later diggers, including the tunnels from a major excavation in the 1960s. The plan, now left in chaos by the weather, was to empty those tunnels completely of their previous loose fill, and then pack them solidly again with chalk. Instead rain is still seeping into the mound, from the summit where the earlier domed repair has already partly washed away, causing damage which can't even be fully assessed until the rain stops.
     A spokesman for English Heritage said: "Our expert archaeologists and engineers are developing a solution to take the project forward, with the aim to stabilise the hill for the long term. We will issue a new programme for the completion of the works as soon as possible."
     Earlier this year, archaeologists found traces of a Roman settlement at the landmark. English Heritage believes there was a Roman community at Silbury Hill about 2,000 years ago. It said the site may have been a sacred place of pilgrimage. The 130ft Neolithic mound near Avebury is thought to have been created some 3,000 years earlier. Parts of the ancient site are thought to be collapsing because of the tunnels dug by archaeologists over many centuries.
     Silbury is not alone. In Hereford, rain has been scouring away parts of a mysterious structure uncovered only a few weeks ago: the Rotherwas Ribbon, a serpentine path surfaced with deliberately burned stones, winding up a shallow hill - slap in the path of an unpopular new road plan.
     English Heritage archaeologists have inspected the site - which some believe is a ritual pathway, almost as old as Silbury - and are considering whether it merits becoming a scheduled ancient monument, which would give it official protection. They described the remains as "extremely fragile". Meanwhile, the rain is washing stones out of the stretch already exposed. Council plans to install a temporary protective cover were abandoned. "The site was so wet we were advised we would do more harm than good," a spokesman said. In any case, the council has now halted work near the site although construction on the rest of the road will continue. It turned down a further option, which was to order an independent inquiry into the matter.

Sources: The Guardian, BBC News (27 July 2007), Western Daily Press (28 July 2007)