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HomeMy WebLinkAbout2560463 - F.I. Received Doc. - Japanese Knotweed Management Plan Japanese Knotweed Management Plan Ronan Boyd, Tullynahinnera, Castleblaney Co. Monaghan Reference Number: KN26002 RECEIVED: 16/04/2026 2 1 Introduction (See attached Map below in figure 1). Figure 1 Location Overview with knotweed stands in yellow. 1.1 PROJECT DETAILS ESC Environmental LTD has been commissioned by Ronan Boyd to formulate a management plan for a site at Tullynahinnera, Co. Monaghan, ITM): 678812, 815551. The area had been previously surveyed by Mr. Peter McCormick, Senior Ecologist at ESC Environmental LTD and non-intrusive ground investigations were carried out. ESC Environmental LTD observed viable Japanese Knotweed (Fallopia japonica) stands both to the west of the site along the drainage ditch and along either side of the road going through the center of the site. The site is to be used for soil infilling of byproduct soil and stone, and a management plan is necessary to ensure the operation of the site while ensuring the control of the Japanese Knotweed on site. RECEIVED: 16/04/2026 3 1.2 Relevant Legislation The regulation of Japanese Knotweed as an invasive species has been implemented through the Wildlife Act 1976 and 2000 and further regulated through the European Communities (Birds and Natural Habitats) Regulations 2011 (SI 477 of 2011). Regulations 49 and 50 of this legislation include legislative measures to deal with the dispersal and introduction of invasive alien species: 'a person shall be guilty of an offence if they: plant; disperse; allow or cause to disperse; spread or cause to grow the plant in the Republic of Ireland'. The list of species in the Third Schedule includes Japanese Knotweed, Giant Knotweed and their hybrid Bohemian Knotweed. Regulation 49 'a person shall be guilty of an offence if they: plant; disperse; allow or cause to disperse; spread or cause to grow the plant in the Republic of Ireland'. The list of species in the Third Schedule includes Japanese Knotweed, Giant Knotweed and their hybrid Bohemian Knotweed. Regulation 50 ''a person shall be guilty of an offence to or intend to; import; buy; sell; breed; reproduce or propagate; offer or expose for sale; advertise; publish a price list; transport; and distribute any plant species or vector material listed in the Third Schedule'. Non-native species subject to restrictions under Regulations 49 and 50 are included in the third schedule of the European Communities [Birds and Natural Habitats) Regulations 2011 (S.I. 477 of 2011). The Third Schedule lists invasive species which include: Japanese Knotweed, Giant Hogweed, Giant Knotweed, Giant Rhubarb, Himalayan Balsam, Himalayan Knotweed, Bohemian Knotweed and Rhododendron. 1.3 Reference documents The following guidance documents and literature sources were consulted during the preparation of this report: • INNSA (2017) Good Practice Management Guide for Japanese Knotweed (Fallopia japonica) • PCA (2018) Code of Practice Management of Japanese Knotweed • National Roads Authority NRA (2010). Guidelines on management of noxious weeds and non- native invasive plant species on national roads • NPWS (2011) Actions for Biodiversity 2011-2016, Ireland's 2nd National • Biodiversity Plan. Department of Arts, Heritage and the Gaeltacht. • Irish Water Report. Information and Guidance Document on Japanese knotweed Asset Strategy and Sustainability 2 Management Methods The following management methods were considered for the Japanese Knotweed infestation at this site. The methods are listed in order of preference with the first (treatment in-situ) being the most preferential option to the last (removal off-site) being the least favored option. RECEIVED: 16/04/2026 4 Avoidance: This method is only possible if the affected area can be avoided, and the knotweed does not pose a threat to buildings or infrastructure during the construction and operational phase of a project. It is strongly advised to follow this with in-situ treatment. This option has been included to allow for an exclusion zone with sufficient buffer zone (7m around the overground plant/stand). The area where the other infestation resides must have an exclusion zone for the duration of the treatment period for stem injection and spraying for the next 4 years if it is chosen to do so. 2.1 Treatment in-situ There were two options considered for treatment in-situ spraying and stem injection. This is the preferred method of treatment for the site. 2.1.1 Spraying The spraying of glyphosate herbicides in the treatment of Japanese Knotweed is generally accepted as an effective method. The Japanese knotweed would have to undergo treatment for at least three years before Knotweed stops regenerating and there is a risk of dormancy of rhizomes when treated poorly or in the incorrect growth period. The most effective time for herbicide treatment is from August to September or before cold weather causes leaves to discolour and fall. Spraying can affect surrounding plants and waterways. 2.1.2 Stem Injection This method is very similar to the spraying method except that the foliage is not sprayed but each individual stem is injected with a glyphosate-based herbicide. This method is targeting the Japanese Knotweed only and limits negative effect on surrounding plants. 2.2 Bund method The bund method involves a shallow bund area of Japanese Knotweed contaminated soil, typically 0.5m deep. The bund can either be raised on top of the ground or placed within an excavation to make the surface flush with the surrounding area. The purpose of the bund is to move the Japanese Knotweed to an area of the site that is not used. This ‘buys time’ for treatment that would not be possible where the Japanese Knotweed was originally located. The construction of the bund is critical, especially if it is likely to be deeper than 0.5m. The aim is to concentrate the rhizome into the upper surface of the bund, where it will grow and be controlled by herbicide. If rhizome is buried deeply, it will become dormant inside the bund and regrow when the apparently clean soil is used for landscaping on the site. 2.3 Root Barrier Membrane The root barrier membrane is used in areas near Japanese Knotweed where the soil containing the Japanese Knotweed does not have to be disturbed to facilitate the proposed development or used in conjunction with excavation to ensure no viable rhizomes can grow after the excavation. It consists of placing a specialised Japanese Knotweed root barrier either vertical, horizontal or both between the building/infrastructure and the affected area. RECEIVED: 16/04/2026 5 Excavation should be conducted under supervision of a Japanese Knotweed expert and transportation should only be carried out by a licence haulier and to a licenced facility. 2.4 Deep burial onsite This option involves the deep burial of contaminated soil on-site to a depth of five metres or more. The material should be sealed within a root barrier specifically designed for knotweed containment. The structure of the excavation and the potential for compaction of the waste soil within it, should be verified by a structural engineer to minimise the risk of settlement within the burial. Alternatively, an underground cell could be constructed to store infested soil permanently and securely by wrapping it in root barrier membrane. This would require the burying at a depth of over 2 metres instead of 5m. The location of the burial area, and detailed working restrictions on or near the burial area should be accurately recorded and relayed to the client to be included in relevant site documentation. 2.5 Off-site Disposal The off-site removal is the least preferred option as it involves movement of soil. The excavation needs to be conducted in a manner to minimise all the risks of spreading of rhizome material during the excavation, loading and transportation. Excavation should be conducted under supervision of a Japanese Knotweed expert and transportation should only be carried out by a licence haulier and to a licenced facility. RECEIVED: 16/04/2026 6 2.6 Summary of Viable Options The table below shows the considerations and decisions in a summary table. ESC Environmental Ltd include a 3-year aftercare/monitoring in their service to ensure no regrowth or spread is taking place. Option Criteria Decision Avoidance Can infested areas of the development site be avoided? The areas to the west beside the drainage ditch are able to be avoided and buffer zones prepared. Herbicide treatment – Stem Injection Can any areas within the development footprint be left undisturbed and treated in the long term? To be used alongside avoidance Herbicide treatment - Spraying Can any areas within the development footprint be left undisturbed and treated in the long term? To be used alongside avoidance Root Barrier Membrane Does the material need to be disturbed? Does the building/infrastructure need to be protected from lateral or vertical rhizome spread? Not needed as the knotweed is concentrated on site and not from outside areas. Avoidance and herbicide treatment will be sufficient for the westmost knotweed. Bund Method Is there space available within the site for a bund to allow treatment over a prolonged period? There is space available to bund the knotweed material which is around the buildings present on site. This is a preferred option for this. Deep Burial – 2m Can the material be buried to a depth of 2 meters? Not a viable option due to the nature of the project being to raise the ground level with soil. Deep burial – 5m Can the material be buried to a depth of 5 meters? Not a viable option due to the nature of the project being to raise the ground level with soil. Off-Site disposal Are other feasible options available? Not being used as there are other treatment options available. 2.7 Recommended Management options Due to the scale and location of the knotweed stands and the nature of the proposed project on site, a combination of avoidance, in situ herbicide treatment, and bunding is recommended. RECEIVED: 16/04/2026 7 3 Management Detailed/Description Due to the nature of Japanese Knotweed, it can never be taken for granted that all rhizomes are removed. Regardless of the chosen method of treatment some best practice measures should be adhered to. • Clearly mark the infested area and allow a buffer zone around the plant/stand • Clear signage to indicate the presence of Japanese Knotweed • Exclusion zones should not be unnecessary entered. • All footwear should be cleaned before exiting the area in a designated cleaning area • Any material and plant/machinery leaving the site should be inspected and dry cleaned in a designated area • All personnel present on site should be made aware of the locations of the exclusion zones and be aware of the risks of working near Japanese Knotweed • Awareness of the Japanese knotweed should be promoted by including the topic in all toolbox talks. 3.1 Inventory of the Site ESC Environmental LTD carried out investigations on the 4th February 2026, consisting of 10 no. stands. Knotweed plants were noted in 2 main areas, west of the site along the drainage ditch area and in the centre of the site along the road and buildings. The area as deemed fit to proceed with the treatment without causing any spread of the infestation once all the recommendations are adhered too. 3.2 Site Specific description of Management Options The proposed treatment within this management plan involves a multi-faceted approach whilst still ensuring that the relevant guidelines and regulations are adhered to and there is no breach of the Section 49 or 50 of the European Communities [Birds and Natural Habitats] Regulations. The treatment of Japanese Knotweed will be supervised and overseen by suitably qualified Environmental Scientist to ensure that the good practice prescribed is adhered to and all waste is removed off site according to the 1996 Waste Management Act and its amendments. The sections below provides a site-specific method description for the chosen treatment options. RECEIVED: 16/04/2026 8 3.2.1 Proposed Methodology 3.2.1.1 Avoidance The knotweed to the west of the site is to be fenced off to prevent further spread of the plant. A buffer of 7m will be adhered to for these stands. The knotweed present here will be treated annually with herbicide, both injection and spraying, until there is no evidence of the species reemerging. 3.2.1.2 Bund Method The knotweed which is beside the buildings and the road will need to be bunded prior to treating on site. This is so the access road can be used during the operation of the facility. A bund is to be constructed in the southern section of the site for the knotweed containing materials. A bund is a shallow area of Japanese knotweed-contaminated soil, typically 0.5m deep. The bund can either be raised, on top of the ground, or placed within an excavation to make the surface flush with the surrounding area. The bund is to be constructed by creating embankments in which to contain the material contaminated with knotweed. This enclosed area is then completely lined with root barrier membrane to prevent the spread of knotweed outside of the prescribed bund. A well-constructed bund should have the majority of the rhizome near the surface, which will encourage regrowth. The base of the bund should be made up of the subsoil layer, which has the lowest amount of rhizome in it. When you have created the base of th e bund, you can place the topsoil over it and spread the surface material over the surface. The depth of the soil within the bund should be between 0.5m deep and 1m deep. The extraction of Japanese knotweed should be carried out using a controlled approach to ensure it does not spread to further areas. Warning signage of excavation should be erected and fencing should be used to limit access. A loading bay should be constructed of stone and geotextile to ensure that heavy machinery moving through the site after extraction will not spread the knotweed further. The bottom of the excavation point should be cleaned using a grading bucket. 3.2.1.3 Excavation Pilot holes should be dug by hand to test the area and soil before excavation via machines. This will inform on the spread of the knotweed and possible depth needed for removal. All personal who are to participate in this excavation must be trained personnel and must work under the guidance from ESC Environmental for correct operating procedures and best techniques for prevention of spread of the Japanese Knotweed . A member of ESC Environmental will always be present on site to ensure the correct removal process is followed. The top and subsoil should be excavated using an excavator and deposited into the bund. All rhizome containing soil will be deposited in the bund for treatment. RECEIVED: 16/04/2026 9 To further reduce the likelihood of spread all vehicles and equipment used at the site will be thoroughly cleaned every night and before leaving the site. No heavy pressure washing is to be used as this could lead to potential rhizome spread around the site. 3.2.1.4 Final Steps After exaction works are completed, the site was backfilled with clean rhizome free soil and the site was thoroughly cleaned as were all machinery used. Dry cleaning was used to minimize the likelihood of any spread after work was completed, A Knotweed expert of ESC Environmental LTD was present to ensure that no rhizome material was left on the buckets or track. When the buckets and machinery were clean, they were given the “all clear” to be removed from the site. Table 1: Chosen Treatment Options Site Preparation The Japanese Knotweed is to be fenced off with a buffer zone of seven metres from the closest above ground stems. No activity is allowed without supervision of ESC Environmental LTD within these zones. This is in line with the relevant guidelines and ensures that there is no possibility that rhizomes from these stands could have spread beyond the exclusion zone. There will be no access to these areas until the Knotweed treatment has been successfully completed. Activity can commence in these areas after the “all clear” from ESC Environmental LTD. Bund Preparation A bund will be prepared by constructing embankments which contain an area lined with a specialised Japanese Knotweed specific root barrier. Excavation A 360 excavator within a containment area will excavate the stand and any nearby top soil and subsoil which is contaminated and will transfer the contaminated soil to the pre-prepared bund. Herbicide Treatment The Japanese Knotweed which is fenced off to the west of the site, and the bunded knotweed will be treated annually with herbicide. This treatment will include both spraying and stem injection. After Care ESC Environmental LTD can include in their service a 3 year after care period. In this case the after care will consist of investigation and monitoring. The site will be inspected for any re - growth. If any re-growth is found this will be included in the treatment plan (stem injection and/or spraying) and an exclusion zone will be implemented where required. Site inspections will be carried out in twice yearly for a 3-year period. RECEIVED: 16/04/2026 10 Supervision and Reporting The works will be overseen be an Environmental Scientist and knotweed specialist of ESC Environmental LTD. The supervision will be carried out by ESC Environmental LTD and the super visor will be on-site for the duration of the treatment and also if chosen the installation of the vertical root barrier. The supervisor will keep a record all activity involved in the treatment of the Japanese Knotweed. Following the completion of the barrier installation, ESC Environmental LTD will issue a completion report. ESC Environmental LTD will report the status of the treatment and monitoring annually to the stakeholders. 4 Conclusions & Recommendations 4.1 Conclusion The site-specific Japanese Knotweed management methods and treatment options are designed to follow the best practice and follow the best practice guidelines and relevant regulations. As in situ treatment is preferred, a combination of avoidance, bunding, and herbicide treatment will be used. Implementation of this Management Plan will ensure that the treatment options are carried out according to the relevant legislation. Exclusion areas are to be set up to prohibit further spread. This management plan provides for the treatment of Japanese Knotweed only within the footprint of the proposed development area RECEIVED: 16/04/2026 11 Appendix A – Site Photos Knotweed stands beside west drainage ditch. RECEIVED: 16/04/2026 12 Knotweed stands along road through east of the site, adjacent to cattle watering area. RECEIVED: 16/04/2026 13 Site photos produced by ESC Environmental Ltd from February 2026 survey. RECEIVED: 16/04/2026