When carrying out a permanent burial of Japanese knotweed on site, Japanese Knotweed Expert will follow the procedure below:
Soil will be sifted and the main stand and rhizomes removed. The soil is then put into a dumper and the soil is spread back into the hole that has been excavated. It is checked again and any rhizomes missed are removed. The root barrier should be UV and animal resistant and guaranteed for 50 years. The guarantee needs to be this long because the Japanese knotweed rhizome can remain inactive for over 20 years. Ideally, the barrier would not contain any joins and would be one large sheet for the entire area.
Japanese knotweed can damage concrete so will easily break through seams if they are not properly jointed. Therefore, if two root barrier sheets have to be joined this should be done by a very competent individual. If the contaminated soil can not be buried at a depth of 5 metres, it can be buried with just 2 metres of uncontaminated soil on top of it. However, the mound of contaminated soil must be totally encapsulated within the root barrier membranes.
Sand or identifying tape should be put on top of the membrane to make it easily identifiable if anyone digs in that area in the future. Ideally, it would be buried where the site is being landscaped and any trees are planted above the stockpiled Japanese knotweed.
Report provided within 48 hours