Invasive Species

Identification and Treatment of Japanese Knotweed and Other Invasive Species

Many non-native plant species exist in the UK without causing a problem, but a few become invasive. Invasive species upset the balance of the ecosystem as they are bigger, faster growing or more aggressive than the native species.

A2 Environmental Consultants Ltd (A2), in carrying out desk study and due diligence site walkovers, are experienced in the identification and eradication of invasive weed species including Japanese Knotweed, Giant Hogweed and Himalayan Balsam. They also employ personnel trained and accredited to undertake herbicide treatments and carryout site specific designs for the remedial treatment and eradication of invasive species.  On impending construction sites, Japanese Knotweed represents a particular risk as tiny fragments of its rhizome can produce a viable plant which can grow as much as 2 centimetres a day and can grow through walls and concrete.  Thus the correct identification of invasive species at an early stage in the development process is important in determining project viability and cost certainty.  Furthermore identifying invasive species at an early stage can substantially reduce the costs associated with treating the problem.

 Invasive Species and the Law
Once invasive species have been identified on a site, their control and treatment is addressed by several pieces of UK legislation which include:

  • The Wildlife and Countryside Act (as amended) 1981,
  • The Environmental Protection Act 1990,
  • The Environmental Protection (Duty of Care) Regulations 1991,

The above legislation puts a Duty of Care obligation on the owner of the land, on which the invasive weeds are growing to control and/or eradicate the problem.  For new developments, the planning process will generally implement planning conditions requiring a detailed eradication and validation programme to be undertaken.

Additionally there is also a body of case law related to Third Party litigation where damages have been sought as a result of a landowner allowing Japanese Knotweed to spread on to adjoining properties.
For Japanese Knotweed, all parts of the plant and any soil contaminated with rhizomes are classified as special waste. Thus where it is necessary to remove spoil contaminated by Japanese Knotweed, the works need to be undertaken by licensed waste carriers fulfilling all Duty of Care obligations. 

With early identification, there are a number of “relatively low cost” control measures available, including herbicide treatments or on-site containment within engineered geotextile cells and barriers. A2 fully understand the development process and can provide full project design and control to help projects stay on schedule and to minimise costs.

Environment Agency guidance currently states that landowners are not legally obliged to remove Japanese Knotweed, unless it is causing nuisance to neighbouring property.  However, it is an offence to plant or cause Japanese Knotweed to grow, in the wild.  The EA have also published a Code of Practice for the management of Japanese Knotweed on development sites.

Herbicide Treatments
A2 have in-house experienced and accredited personnel capable of undertaking herbicide treatment of invasive weeds utilising a variety of application techniques deemed the most appropriate for the site.  Methods employed include traditional spraying techniques as well as stem injection which is less weather dependent and only affects the targeted plant which makes it suitable for sensitive habitats.

On-site Burial
A2 has designed containment cells constructed using barrier membranes to provide engineered containment cells for the on-site retention of Japanese Knotweed infected soil.  Membranes used include root barriers incorporating growth prevention materials and High Density polyethylene (HDPE) sealed burial cells.

Off-Site Disposal
Where there are no other alternative treatments available, due to project time constraints, surplus excavation spoil or additional contaminated spoil issues, off-site spoil removal may be the only solution.  A2 can provide personnel experienced in full site remediation design in which the removal of ‘contaminated’ spoil is undertaken in a controlled manner, such that all waste streams are appropriately segregated to minimise additional waste.  By correctly segregating waste streams the ultimate disposal costs are reduced.  Due to our knowledge of the waste industry, A2 personnel can assist with obtaining competitive disposal rates, applying for and completing consignment notes, and provide advice on satisfying Duty of Care obligations. Although off site disposal is the most expensive option, our knowledge can help to minimise costs.

Record Keeping and Validation
A2 diligently provide records of all pesticide treatments for each area and treatment including Ordnance Survey Coordinates which is particularly useful for return visit treatments and input to GIS.  We are experienced in the production of COSHH and Environmental Risk Assessment and provide full documented protocols and method statements.  For development projects we can provide fully documented validation reports for submission to the relevant local authority to confirm compliance with agreed remediation scheme.


A2 Environmental Consultants Ltd | Registered in Scotland - 374917

53 Bothwell Street, Glasgow, G2 6TS | TEL: 0141 226 6945