THE LONDON 2012 Olympic cycle park site must be monitored for radioactivity during construction, it was revealed this week.
Historical data points to radioactive trade waste buried in the area that the Velodrome will be built on, but nuclear experts describe the risk posed to contractors digging up the site as minimal.
'I don't think there would be any need to worry about using special shallow foundations to avoid disturbing the waste, ' said one expert.
'All that will be needed is someone onsite checking radioactivity levels.' Several 40?gallon steel drums containing demolition waste contaminated with thorium were buried on the site in 1959 (see feature p24).
An Atkins' investigation into radioactivity on the site in 1994 was inconclusive, as thorium is naturally occurring in granite, also present in the ground on the site, and levels detected were not higher than normal.
However, Atkins only dug trial pits to a depth of 6m and the consultant's report, obtained by NCE, claims that the waste could be buried as deep as 11m.
Any radioactivity may be shielded by the remaining 5m of earth yet to be investigated.
'Piled foundations for a structure such as the Velodrome could penetrate the waste if it is there, ' he added.
'But thoron, the radioactive gas that thorium produces when it disintegrates, decays in under a minute, so as long as contractors are wearing the correct PPE, it's unlikely they would be harmed.'