Knotweed sets Olympics £70m challenge
The organisers of London’s 2012 Olympics will this week reveal that knotweed has invaded the sites of two of the main arenas — leaving the games with a clear-up bill which experts predict could top £70m.
Surveys of the site in Stratford, east London, have revealed a 10-acre swathe of Japanese knotweed under the proposed velodrome and aquatic centre. The plant spreads so aggressively that it could undermine stadium walls and crack concrete concourses unless every trace is removed. The full extent of the contamination of the site for the games, including unexploded bombs and toxic chemicals, is still being assessed.
The Olympic Delivery Authority (ODA) has already identified mercury, lead and petro-chemicals in the soil, as well as asbestos in derelict buildings. There are also as many as 60 unexploded bombs dropped by the German Luftwaffe during the second world war.
Details of the scale of the task to decontaminate the site follow the announcement by Tessa Jowell, the culture secretary, that the budget for the Olympics has risen to £9.3 billion.
The ODA insists that work to prepare the Stratford site is on time and the costs are within the £220m set aside for clearance of the contamination.
The toughest task is likely to be removing the knotweed. Every part of its roots, which can burrow 10ft deep, has to be removed. Digging out and disposing of the plant in an area of just six square yards can cost as much as £40,000 because high levels of bio-security are needed to ensure that fragments of the plant are not dispersed.
It is understood that in other parts of the site the ODA plans to use herbicides, although this can take years. Mike Clough, managing director of Japanese Knotweed Solutions, said: “Officials have been talking about the problem of Japanese knotweed on the site for two years, but the chemical treatments take between three and five years to be effective.”
The knotweed was introduced from Japan as an ornamental plant in the early 19th century. Its stem can be as thick as a man’s thigh and it grows at the rate of 1ft every 10 days.
To date, the ODA has surveyed two-thirds of the 615-acre site by drilling 1,000 bore holes. Sources admit that the contamination is “a serious problem”.
The bomb disposal industry is concerned that contracts to remove unexploded ordnance have not yet been awarded despite a timetable which demands that construction on the main 80,000seat stadium and the two swimming pools starts by the summer of 2008.
Jack Lemley, former chairman of the ODA, resigned last year citing deep concern that contamination “has been left untackled for too long”. The ODA denied this.
Workers began cutting and burning the bamboo-like knotweed last week. Other infestations will be treated with high-powered weed killer or dug out and transported to landfill.
Robert Booth, The Sunday Times, March 25, 2007
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