Commercial Knotweed Removal

Excavation and off-site removal or “dig and dump” is regularly used on land where there is a requirement for a quick solution. The resulting spoil must be treated as controlled waste (Environmental Protection Act 1990) and due to a tightening up in the regulations regarding the use of landfill sites, there are a limited number of landfill sites in the country that will receive this waste. TCM can offer cost effective project management of “dig and dump” projects, by reducing the quantity of material for disposal to landfill via detailed monitoring. This method can be backed up by guarantee, and can result in savings of around 50% of traditional “dig and dump” volumes.

This method utilises herbicides and the efficacy of the treatment depends upon a number of variables, including:

• Dosage rate
• Chemical composition
• Application method
• Weather conditions during and after spraying

The cost of herbicidal treatment is a fraction of “dig and dump” and may be appropriate where eradication time is unlimited by factors such as a construction programme.

Should there be areas within a project that need immediately developing, it is possible to excavate and remove the Japanese Knotweed to a different area on the same site. We have used this method many times and it continues to be a popular choice for phased developments. The contaminated soil and vegetation is then protected by a suitable membrane, with an applicable maximum depth and treated using the TCM system:

• The larger sections of rhizomes will be manually removed which will allow for more effective treatment of the contaminated remains.
• The larger sections will be stored on site and desiccated (dried out) prior to removal to landfill site or incineration on or off site.

Due to the chemicals used in this treatment, it may not be possible to use the soil for landscape areas where tree and shrub planting will occur for approximately of 12 months post-eradication. However, grass species, turf and bulbs will establish rapidly and can be laid immediately after eradication of the Knotweed has been completed.

This system involves the excavation of the Japanese knotweed from the area, with the contaminated spoil being buried to a pre-determined depth. The excavation of this area will be under the supervision of our experienced TCM team, and the rhizomes will be accurately followed to reduce the amount of material excavated. A suitably sized burial pit will be identified from the contaminated spoil and full GIS mapping will be undertaken to show both the areas of excavation and the burial area. The burial pit will be lined with a bespoke membrane, with the entire joint being heat sealed by a team of experts. Only then will the contaminated material be placed inside the cell. Once the cell has been filled, the membrane will be placed on top and again the joints are sealed.

Soil screening is a mechanical process carried out on site which allows Japanese Knotweed contaminated material to be reused on site. The aim of the system is to allow contaminated soil to be used on site immediately; eliminating the need to take any material to landfill and importing backfill for excavations that have been undertaken to remove Japanese Knotweed. Rhizome that is removed from the soil can be sent to landfill. The treated soil can be then re-introduced on site as fill (depending on the geotechnical suitability) or in soft landscaping areas.