Dig and Off-Site Disposal
The purpose of off-site remediation is to clear the site completely of all plant material and infested soil, for safe and controlled disposal. This is the least favoured option from the point of view of both cost and biosecurity, but may be necessary in situations where development is occurring on small or difficult sites, where there is going to be full site coverage, or where ground conditions and substructure design cannot be adapted to accommodate the residual spoil in situ.
In the case of Japanese Knotweed, for example, to ensure that all viable plant material is removed, it may be necessary to excavate up to 7m horizontally in all directions from the perimeter of the infestation, and to a depth of 3m. Having to draw this volume of soil off-site, with the attendant transport costs, the risk of inadvertent dispersal, and the limited number of licenced repositories in Ireland, makes off-site disposal unattractive. Nonetheless, there are many circumstances where full or partial removal of infested material from site will remain the only viable or practical option.