Are AGS Members aware of the potential impact Japanese Knotweed (JKW) may have on the development of sites?
If this is not identified when carrying out walk over surveys and ground investigations, the additional cost to the client of clearing the plant from site and the possibility that the ‘Ground Investigation Specialist’ could be blamed for not identifying it in the first place as a potential ‘contaminant’, could result in significant potential liabilities, e.g. A site in the Midlands is currently clearing JKW off site at a cost of over £250,000, as an extra over cost!
The AGS and current British Standards for ground investigation (reporting guidelines) do not appear to specifically cover such potential ‘contaminants’. Should we not be providing advice to both Geotechnical/ Geo- Environmental specialists/ Clients etc in how to identify these invasive plants or at least provide them with guidance as to what specialists should be appointed to identify and deal with such problems? Is this part of our role? What do members think? The EA currently provide guidance notes on their web site www.environment-agency.gov.uk.
In addition the implications of a ground investigation contractor spreading the JKW by vehicle wheels/tracks, samples etc could again be costly. Whilst this weed is widely distributed in Cornwall and Wales, its encroachment into other parts of the UK is rapid.
Any comments or discussion back would be appreciated.
Chris Eaton, Geotechnical Developments (UK) Ltd
A Knotty Problem
Japanese Knotweed is an invasive perennial that can hinder the growth of many native species of plant. It can grow to around 3m high and expands rapidly once it takes hold of a site.
Japanese Knotweed was introduced to the UK during the 19th century as an ornamental plant and can be spread easily from the movement of contaminated soil. The plant is characterised by thick canes with red shoots and bears white flowers. It is notoriously robust and can survive being cut back due to an extensive underground root system.
The Wildlife & Countryside Act of 1981 makes it an offence to spread Japanese Knotweed and any excavated soil that is taken off site must be disposed of at a licensed landfill site.
The Environment Agency website: www.environment-agency.gov.uk contains very useful information about knotweed, how to deal with it, and what precautions need to be taken if it is encountered on site