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Knotweed Excavation & Burial

One way to manage the impact of Japanese knotweed, especially where it is preventing development on a construction site (commercial or private), is to physically remove it.  This may sound simple enough, but skill and experience are key to achieving a successful outcome when considering the excavation and burial of Japanese Knotweed. 

As much as excavation and burial may seem an instant solution (especially on development sites), experience and awareness of best practice are crucial to ensure a successful outcome. For this reason, we strongly recommend contacting a PCA member for some expert advice; to survey the site, discuss the options and present detailed proposals.

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Knotweed excavation and buriel - Property Care Association

Knotweed excavation & burial methods

1. Excavation & licenced transfer to Landfill 

Excavation & Licenced transfer to Landfill if the site has no space or facilities for on-site remediation (screening, burial, incineration see below) and/or the client wants a simple off-site solution, removal of waste soils to landfill may be the only available option.

2. Excavation & on-site cell burial

One way to avoid landfills is on-site burial and this is often done on larger sites. Burial to depths of 5m+ do not need encapsulation but shallower burial cells (minimum 2m depth capping) can be formed using root resistant barrier membranes.  

3. Excavation & Soil Screening

In both the above cases the volume of soil can be reduced using soil screening techniques (which removes, via sieving, most larger rhizome fragments) but the screened soil will still contain smaller fragments so the ‘Controlled waste’ soil classification doesn’t change.  Despite this, the Government’s Regulatory Position Statement RPS 178 states that screened soil can be used for landscaping as long as locations are defined and accessible for monitoring and/or future treatment. 

Best practice for knotweed excavation & burial

The ‘art’ of excavating Japanese knotweed has been developed over many years and the Environment Agency published a Code of Practice in 2006 to guide developers, contractors and waste companies on the best approach. This was reviewed in 2013, but is no longer supported (so no longer has official status as formal Guidance) .  

The PCA however, has published a number of useful documents within our invasive weed technical library.  Our Code of practice “Management of Japanese knotweed” explains the pros and cons of excavation over other methods of control (to summarise; very effective but also, usually, the most expensive approach and not necessarily the best environmental option if soils end-up in landfill). 

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Other important considerations regarding excavation & burial

On commercial sites (land remediation) the duties and responsibilities of those managing Japanese knotweed on sites include various obligations under the Environmental Protection (Duty of Care) Regulations. This requires the expertise of someone that can verify actions by collating and retaining legally required information, specifically the movement of waste materials, as recommended in our Guidance Note “Verification reports following excavation”

Guidance documents to help support you

Important advice required to manage excavation projects safely and design burial cells (if the site is suitable) are given in our Guidance Note “Safe excavation and burialand more general advice about excavations and the use of root barrier membranes (to manage residual risks of knotweed rhizomes spreading) is available in our Guidance Note “Root Barrier and Japanese Knotweed Remediation".

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Videos you may be interested in

Want to learn more about Knotweed Excavation & Burial?

For those interested in learning more about Knotweed Excavation & Burial, there is a variety of PCA training options for surveying professionals as well as technical/trade professionals. 

Use the search tool below to find available Knotweed Excavation & Burial related training courses or simply go to our training & qualifications section.  Alternatively, if you want to chat to someone, contract our training team on 01480 400 000 or contact them online.

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