Our brief was to advise on and implement a strategy to deal with a stand of Japanese knotweed which was within the construction footprint of a new treatment facility at Hogsmill Sewage Treatment works.
What we did
Using a 14 tonne excavator and two articulated dumpers, we excavated the Japanese knotweed stand and moved it and associated contaminated soil to a designated area on the site. We stockpiled it onto root barrier membrane which prevented it contaminating the ground underneath and also shaped it to blend in with the existing landscape. This was away from the construction area so that any re-growth of Japanese knotweed could be treated with herbicide over a two year programme.
We provided an in-house Japanese knotweed clerk of works, who ensured that the excavation continued until rhizome fragments were no longer visible. He also monitored the dumpers to ensure that they were kept at a safe load to avoid contaminated material spilling during transportation.
We put in place bio-security measures to stop the spread of contaminated material. This included the installation of Heras fencing and signage in order to exclude unauthorised contractors and personnel from the works area. In addition, washing stations were used to clean boots and plant prior to leaving the site.
The Japanese knotweed stand was successfully moved and stockpiled. The work was completed ahead of schedule, enabling our client to get a head start on their construction programme. In addition, we were pleased that our site supervisor was praised by our client on his management of the works.