Knotweed survey and treatment contract leads to further works
On this contract we completed extensive invasive weeds surveys across a large part of the port site and surrounding coastline, which identified large areas affected by Japanese knotweed and hybrid knotweed. This was followed up by multiple seasons of herbicide treatment across the affected areas, which was to be ongoing for a few more seasons due to the scale of the infestation. Further works were awarded following the successful outcome of the project.
The site
The client is part of the UK’s largest ports group and the area requiring surveying totalled 113 hectares, split into one large area and several smaller areas around the port. Much of it was overgrown brownfield land, abandoned following the decline of the dockyard’s former businesses. Considerations were factored into the risk assessment such as the presence of reptiles and protected plant species, preventing herbicide spraying in those locations. There were also several areas close to the dock edge where spraying required a water license, and other access limitations such as land boundaries and active business sites.
Japanese Knotweed in one of the sub-sites
Project overview
The first phase of the contract was to conduct an invasive weeds survey of the main area (H) and 6 smaller areas (A-D, F, G and J). This was carried out in sections by our surveying teams and identified the presence of Japanese knotweed and hybrid knotweed across the site, totalling 90,000m2 requiring treatment. Due to the scale of the site, and the presence of the reptiles, rare plants and open water bodies, a herbicide treatment plan was designed specifically for each area (further split into sub-areas where required) to best tackle the main stands whilst protecting the sensitive receptors.
The works
To date, herbicide treatment of Japanese knotweed has been carried out on three consecutive seasons. In order to cover the large site as efficiently as possible, a 5 person team of herbicide sprayers has tackled the site one area or sub-area at a time. Spraying was targeted to aply only the active knotweed growths with additional care taken to ensure that spraying did not drift onto non-target species.
The project took 3 weeks to carry out foliage spraying of all the identified Japanese knotweed stands within the identified treatment areas.
Parts of the site not suitable for spraying due to proximity to open water, or requiring more rapid treatment to facilitate redevelopment works, were earmarked for excavation instead of herbicide treatment. Japanese Knotweed Ltd was also awarded these excavation works, and has since been awarded a new contract to carry out further excavation works in coming seasons.
During the winter, brush cutting (removing old canes) and other vegetation clearance has been carried out to improve access to the actively growing stands and visibility of treated areas, where bonsai growth may otherwise be concealed. To protect the rare plants and reptiles, brush cutting was not carried out lower than 30cm from the ground.
The team spraying Japanese knotweed foliage with herbicide
Treating Japanese knotweed in another part of the site.
The outcome
To date, the treatment team has successfully completed three seasons of herbicide spraying works in all 7 areas and sub-areas with Japanese knotweed and hybrid knotweed growth across the port site. Several stands not suitable for herbicide treatment due to the presence of sensitive receptors have already been successfully excavated by our team, with the client suitably satisfied with their performance to award us a contract for future excavation works for the following year. The herbicide spraying teams will also return to the site in the following year to carry out more spraying works, as per the ongoing knotweed management plan, until the infestation is under control.
If you have a large, overgrown site requiring a team with experience working on brownfield and post-industrial land and you would like a similar survey carrying out and a Japanese knotweed treatment plan putting into place, please get in touch with our team.