Permanent burial of Japanese knotweed normally occurs when there is not enough time to treat it with a systemic herbicide. Usually, this is due to time constraints from builders, etc. We use permanent burial when the site needs to be cleared quickly and there is a large enough area around the infestation for the weed to be excavated and buried. The benefits are that it keeps the costs of dumping down, whilst the negative is that the hole is typically over 5 metres deep and therefore requires large excavators to be on site.
The Process for Permanent Burial of Japanese Knotweed
- 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 break through 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.
The best practice for Japanese knotweed treatment is herbicidal. However, if you are under time constraints and would like to receive more information on how we can move your project along with Japanese knotweed excavation and removal, please contact us, we will be happy to help.